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What the Weather Carries

A hot northerly in October, a shallow night sky, a storm that arrives without rain — and what each of them does to skin that is already working hard. Plus the parts of this story that belong to asthma and anaphylaxis, and why they are not separate stories at all.

There is a particular kind of Adelaide spring day that anyone with reactive skin will recognise before they can explain it. The wind swings around to the north. The air goes thin and hot and slightly gritty. By mid-afternoon your face feels tight in a way that moisturiser doesn’t quite fix, your eyes are scratchy, and the patch on your inner elbow that has been quiet since August is suddenly, insistently there again.

Most of us file that under “hay fever weather” and move on. But the actual chain of events between a paddock north of the city and the skin on your cheekbones is far stranger and more specific than the phrase suggests — and understanding it turns out to be genuinely useful, because it tells you when the load is high, why the usual advice is often wrong, and what is actually worth doing about it.

This piece walks through that chain. It covers where pollen comes from and what the weather does to it; the odd nocturnal phenomenon where pollen lifted high during the day settles back down at night under a sky that has effectively lowered its ceiling; why rain does not simply “clear the air”; and what all of that means for skin. Because the same weather also drives asthma and, in ways that are only now being measured, tips the balance in food allergy too, those threads are here as well — not as scare material, but because they are the same story told in different tissue.

A note before we start: this is written for education and curiosity, not as medical advice, and nothing in it is a treatment for anything. Where the science is genuinely unsettled — and in this field a surprising amount of it is — this piece says so rather than tidying it up.

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Five Things the Weather Does to Pollen

Popular writing treats “the pollen count” as one number that the weather pushes up or down. It is actually five separate processes, each with its own drivers, running on completely different timescales — from months to minutes. Once you can see them separately, a lot of confusing advice starts to make sense.

1. Production — the season is decided months before it starts

How much pollen exists at all is settled long before any of it is in the air. In Melbourne, where the records run deepest, the total seasonal pollen load correlated strongly with that year’s spring rainfall — a correlation coefficient of 0.79 across nearly two decades.¹ Wet winters and springs grow more grass. More grass makes more pollen. It is that direct.

Which is why Asthma Australia flagged the 2025 Adelaide season in advance: a wetter-than-average winter had left soil moisture higher than the previous year, particularly through the Mount Lofty Ranges, setting up the conditions for a more intense and possibly longer grass pollen season.²

There is a longer trend underneath this too. In Brisbane, the seasonal grass pollen index measured roughly three times higher in 2016–2020 than in 1994–1999, and days at or above 50 grains per cubic metre more than doubled — alongside higher maximum temperatures and carbon dioxide rising from 360 to 404 parts per million over the same interval.³

A “bad year” is not superstition. The load your skin meets in November was partly decided by rain in June.

2. Release — the daily clock, and why the morning advice is wrong here

Grasses release pollen on a daily rhythm governed by temperature, dew and humidity. Warm, dry, sunny mornings following a dew-free night favour release; wet or cold mornings delay or suppress it.

But release and exposure are not the same thing. Melbourne’s average peak in airborne grass pollen falls around half past five in the afternoon — hours after the grass actually let go.¹ The reason is atmospheric, and we will come back to it, because it is the key to the night-time story.

This matters practically. The widely repeated advice that “pollen is worst first thing in the morning” comes from northern-hemisphere tree pollen and does not match Australian grass pollen measurements at all well. If you have been rearranging your walks on that basis, the evidence points somewhere else.

3. Transport — the daily count is mostly a question of wind direction

Day-to-day, what matters most is not what is flowering near you but where the air has come from. In the Melbourne record, extreme days (above 100 grains per cubic metre) and high days (50 to 100) occurred under winds of continental origin. Low days, under 20, occurred under winds of maritime origin.¹

ASCIA makes the same point nationally: coastal counts are lower where sea breezes dominate and higher where prevailing winds blow in off inland grasslands, and South Australian counts are especially variable depending on wind patterns.⁴

For Adelaide the translation is immediate. A hot northerly in late spring is an air mass that has crossed the Adelaide Plains and the pastoral country beyond it. A cool south-westerly off Gulf St Vincent is not. Same city, same date, entirely different day for your skin.

4. Concentration — how much sky the pollen is stirred through

The same amount of pollen released can produce wildly different exposure depending on the depth of air it is mixed into. Think of a spoonful of cordial in a bucket versus the same spoonful in a glass.

Every one of the ten most extreme pollen events in the Melbourne record occurred under an average downward vertical wind anomaly in the surface boundary layer — subsiding, stagnant air that holds pollen down near the ground rather than dispersing it upward.¹ Modelling of the 2016 Melbourne event similarly found most available grass pollen sitting within about 40 metres of the surface.⁵

This is the lever nobody talks about, and it is the one that produces the worst days.

5. Transformation — when pollen becomes something much smaller

A whole ryegrass pollen grain is about 30 to 40 micrometres across. At that size it is filtered by the nose, and it lands — on skin, hair, clothes, eyelashes. It does not reach the lower airways.⁵

Under the right conditions, though, a single grain can rupture into roughly 700 sub-pollen particles of about 600 nanometres each. These fragments still carry the major allergens, they fall so slowly as to be effectively suspended, and they are small enough to reach the deep lung.⁵ Other reviews put the sub-pollen particle range at 0.03 to 5 micrometres.⁶

Air pollution does something similar without any storm involved. Ozone, nitrogen dioxide, particulates and sulphur dioxide stick to the oily outer surface of pollen grains and cause the wall to thin, shrink and rupture, releasing allergen-bearing granules under 5 micrometres. They also chemically alter the allergen proteins themselves — nitrating and oxidising them — which increases their potency and acts as an immune adjuvant.⁷ A hot, still, high-pollen day in a city is usually also a high-ozone day, and the two do not simply add up. They multiply.

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The Pollen Rain: Up in the Daytime, Down at Night

This is the part of the story that most people have never heard, and it explains an experience an enormous number of allergy sufferers report and are quietly told they must be imagining: symptoms that get worse in the evening and overnight, indoors, hours after any sensible pollen exposure should have ended.

What the air does over the course of a day

On a sunny day the ground heats, and the warm air above it rises in great slow thermals. This churning creates what meteorologists call the mixed layer — a body of well-stirred air that can grow to a kilometre or two deep by mid-afternoon. Anything light enough gets carried up into it, pollen included — though lidar studies that measure the atmosphere in vertical slices find the pollen layer does not usually reach the top of the boundary layer, most likely because gravity keeps pulling it back down.⁸

Then the sun goes down. The ground cools quickly, the thermals stop, and the atmosphere stops stirring. What forms instead is a stable, shallow nocturnal layer near the surface — often only a few tens or a couple of hundred metres deep. Above it, the air that was mixed during the day is left behind as what is called the residual layer, still holding whatever it was carrying.

Two things then happen at once. The pollen that was aloft cools with the air and begins to settle back down. And the layer it settles into has become dramatically thinner. The ceiling, in effect, comes down.

The same amount of pollen, pressed into a fraction of the sky it had at three in the afternoon.

That combination — descent plus compression — is why Melbourne’s grass pollen peaks at around half past five rather than at the moment the grass releases it,¹ and it is why the atmospheric researchers measuring pollen with lidar find their instruments seeing almost nothing overhead at night while the ground-level trap is still catching plenty. The stable night layer is often shallower than the lidar’s minimum detection height of about 225 metres.⁸ The pollen has not gone. It has come down to where you are.

How high, and how far, really?

It is worth being accurate here, because the popular version of this story overstates one part of it.

Pollen genuinely does travel long distances, and the night-time arrival of distant pollen is well documented. In a Polish study of more than 2,000 high-pollen days, ragweed — which barely grows locally and arrives almost entirely from Ukraine and Hungary — recorded higher night-time than daytime concentrations on around 60 per cent of days, with peak night levels running more than 30 per cent above daytime peaks.⁹ That is long-distance transport arriving after dark, and it is precisely the phenomenon described above.

For grass, the picture is more local. Grass pollen grains are heavy for their size and fall relatively fast — a deposition velocity of about 4.6 centimetres per second — which limits how far whole grains can travel before gravity wins.¹⁰ Trajectory work in the UK, mapping grassland against measured concentrations, found that source areas out to about 30 kilometres mattered for an urban monitoring site, while for a rural site the important sources sat within just 2 to 10 kilometres.¹¹ Tens of kilometres, in other words — not hundreds.

So the honest version is this. Grass pollen is not routinely crossing continents. But it absolutely is being lifted hundreds of metres into the air above the plains during the day, carried tens of kilometres on the wind, and then delivered back down to ground level in the evening as the atmosphere settles — arriving at your house at the hour you have opened the windows to let the cool change in.

The same Polish dataset found elevated night-time levels for grass, birch and alder on roughly 35 per cent of high-pollen days.⁹ Roughly one night in three. That is not a rare curiosity; it is a regular feature of the season that almost nobody is warned about.

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Why Rain Doesn’t Clear the Air

“It’ll be better after the rain” is one of the most confidently repeated pieces of allergy folklore, and it is only about a third true.

Steady rain does scavenge pollen out of the air as the drops fall. That part is real, and during and briefly after a decent soaking, counts genuinely drop. But two other things happen that complicate the picture considerably.

Fungal spores come in two opposite kinds

This is the distinction that consumer allergy writing almost always misses, and it explains a great deal.

Dry-air spores — Cladosporium and Alternaria, the two biggest outdoor mould allergens — are released and stay airborne in warm, dry, breezy conditions. In a study of 19 convective thunderstorm days, their concentrations rose considerably before the storms arrived, tracking rising temperature and ozone, then fell during and after the storms as humidity climbed. Levels on thunderstorm days were consistently very high — above 50,000 spores per cubic metre for Cladosporium and above 7,000 for Alternaria.¹²

Wet-air spores — the ascospores and basidiospores — do the exact opposite. They are actively discharged by moisture, and they rise sharply after rain.

So rain does not clean the atmosphere. It swaps one airborne population for another. If you feel worse after rain rather than better, you are not being difficult, and you are not imagining it — you may simply be reacting to the population that rain releases rather than the one it removes.

And the hours before a storm can be the worst of all

The gust front that runs ahead of a spring storm is a wall of air being pushed out and down. It lifts dust, pollen and spores off the ground and drives them along in a dense front — before a drop of rain has fallen. The advice from the National Asthma Council is unambiguous on this point: avoid being outdoors just before and during thunderstorms in spring and early summer, especially during the wind gusts that precede the rain.¹³

Which is the reverse of what most people instinctively do, which is to stay out enjoying the cool change and go in when it starts raining.

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The Four-Stressor Day

Now to the part that concerns skin directly — and the reason this piece exists on a skincare blog rather than a respiratory one.

The airway story gets the headlines because thunderstorm asthma kills people. The skin story is quieter. But it is matched to everyday weather rather than to rare events, it affects far more people far more often, and it is almost entirely absent from public messaging.

Here is what is actually happening. On a hot, dry, windy, high-pollen Adelaide day, skin that is already reactive is meeting at least four stressors at once, and they are genuinely independent of each other.

Stressor one: things are landing on you

Your skin is the largest surface you present to the air, and whole pollen grains — too big for the lower airways — deposit on it readily. Face, neck, upper chest, hands, forearms. Exactly the places that are uncovered.

This has a proper clinical name. Airborne contact dermatitis is the recognised dermatological term for acute or chronic dermatitis on air-exposed skin, caused by substances released into the air and settling on it. Its characteristic distribution — face, neck, upper chest, hands, wrists — is the giveaway, and plant material including pollen is an established cause, distinct from a light-triggered reaction.¹⁴

And this is not merely correlational. In an environmental challenge chamber — a sealed room where pollen exposure can be controlled precisely — grass pollen exposure produced eczema flares on the exposed skin of sensitised patients, along with a systemic rise in inflammatory mediators including IL-4.¹⁵ That is an experiment, not an observation. Airborne pollen makes eczema worse.

Stressor two: what lands is chemically active

Pollen is not inert dust. It arrives loaded, and it does three separate things.

1. It carries enzymes that pick at the barrier. Pollen contains proteolytic enzymes capable of degrading tight junction proteins — E-cadherin, claudin-1, occludin, ZO-1 — the molecular rivets that hold a barrier layer closed.^6,16 This is best documented in airway lining, and the same protein family builds the tight junction layer of the epidermis. Worth being straight about: the direct skin evidence is thinner than the airway evidence. It is mechanistically plausible and partly extrapolated, not proven.
2. It generates oxidative stress on its own. Pollen grains carry their own NADPH oxidase activity and produce reactive oxygen species in the tissue they land on, entirely independently of the allergen proteins — an acute chemical “danger signal” to the surface it settles on, arriving before any inflammatory cells do.¹⁷ Like the protease point above, this was established in airway tissue rather than skin.
3. It releases immune-tilting lipids. Pollen sheds bioactive lipid mediators that push the human immune response toward the Th2 pattern — the same polarisation that underlies atopic dermatitis.¹⁸

Together these explain something that confuses a lot of people: you can react to pollen on your skin without being “allergic to” that pollen in the classical, allergy-test sense. Part of the effect is barrier chemistry and irritation, not antibodies.

Stressor three: the air itself is pulling at the barrier

Separately from anything landing on you, dry air is doing its own work. Abrupt decreases in environmental humidity disturb the skin’s permeability barrier, and ambient humidity is an established determinant of barrier function in both healthy and diseased skin.¹⁹

One honest complication, because this field is less tidy than skincare writing usually admits: the relationship is regionally specific rather than universal. In an infantile eczema study, warm low-humidity conditions were associated with a 23 per cent reduction in incidence, while higher atmospheric pressure was associated with an increase.²⁰ “Dry air is always bad” is too simple a rule. What is consistent is that rapid change in humidity is disruptive.

Particulate pollution adds to it independently. In Singapore, fine particulate matter at the 90th percentile was associated with a 10 per cent increase in eczema consultations compared with median levels.²⁰

Stressor four: heat and sweat

Sweat is an established trigger of itch in atopic dermatitis, through mechanisms entirely distinct from allergen exposure.²¹ On a 35-degree northerly day you are sweating into a barrier that is simultaneously being pulled at by dry air and picked at by pollen enzymes.

Which is why the day feels the way it does

Four separate mechanisms, arriving together, on the same afternoon. Not one problem with four names — four problems that happen to share a weather pattern.

If your skin feels unreasonable on those days, it is having an entirely reasonable response to four things at once.

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When the Storm Changes Everything

The extreme version of all this is epidemic thunderstorm asthma, and South Australia has a direct stake in it.

What happened in Melbourne

On 21 November 2016 Melbourne experienced the largest recorded epidemic thunderstorm asthma event anywhere in the world.²² In the 30 hours from 6pm, respiratory presentations to Melbourne and Geelong public hospitals rose by 672 per cent — an excess of 3,365 presentations against the three-year average.²² There were 476 excess asthma admissions, roughly a tenfold rise.²⁴ Thirty-five people needed intensive care. Ten people died — six of them of Asian or Indian descent, a disparity nobody has yet fully explained.^6,22,24 Triple Zero calls ran 147 per cent above forecast between 9pm and midnight and took thirteen hours to return to normal.²³

The day itself: 35 degrees, hot dry northerly winds, high ryegrass pollen off the grasslands north and west of the city, and a gust front sweeping through in the early evening.²³

Who it happened to — and this is the part worth knowing

Most of the people who presented did not have a diagnosis of asthma. But almost all of them had seasonal allergic rhinitis — hay fever.¹³ Allergic rhinitis is present in something like 70 to 100 per cent of thunderstorm asthma cases.²⁴

The severity pattern was different again. Everyone who was admitted to intensive care or died did have current doctor-diagnosed asthma, and most of them were not using a preventer inhaler.¹³ Mean age of emergency presentations was 32. There was a notably elevated risk among people of Asian and Indian background.^13,24

The mechanism is less settled than you have been told

The textbook explanation is that pollen is drawn up into humid air at the base of the storm, absorbs water, bursts osmotically, and the downdraught delivers the fragments to ground level. Recent reviews still describe it this way, citing high humidity, strong convection, and a 250 per cent increase in ruptured grass pollen particles measured during the 2016 event.^6,16

But an atmospheric modelling study tested eight candidate rupture mechanisms against that event and found the humidity explanation performed badly.⁵ Relative humidity that day was very low throughout the atmosphere — 18 per cent at the surface. A humidity-threshold mechanism produced its rupturing overnight rather than during the daytime storm, and would generate constant false alarms if used to forecast. The mechanisms that best matched the timing and location of the emergency calls were high wind-speed thresholds and lightning-triggered rupture. And the observed peak in whole pollen occurred about 20 hours before the storm.⁵

So: we know storms can turn a nose-and-skin allergen into a deep-lung one. We do not yet know precisely which part of the storm does it, and the most-repeated explanation does not fit the worst event on record. That is a live scientific question, and saying so is more useful than repeating a tidy answer.

South Australia, specifically

In 2025 the first scientific investigation of thunderstorm asthma in South Australia was published.²⁵ Looking across six SA regions from 2003 to 2017, using ambulance callouts, emergency presentations and hospital admissions, it found:

• Severe thunderstorms were associated with increased asthma risk in the Adelaide Metropolitan and Hills region — particularly among children.
• Seasonal trends in childhood asthma were evident in the warmer months.
• Daily pollen count was not a significant mediator of the association, which points toward mechanisms beyond simple pollen availability and echoes the modelling finding above.
• Pollen data existed for only one location in the entire state — a real limitation on what we can say about SA.

So yes: it happens here, including in the Hills, and children appear to be more affected. Victoria runs the country’s only operational epidemic thunderstorm asthma risk forecast, from 1 October to 31 December, combining weather modelling with a ryegrass pollen forecast verified by automated counters, on a green–orange–red scale.²⁶ I could find no equivalent public risk forecast for South Australia.

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Skin and Asthma Are the Same Story

It is tempting to treat eczema as a skin problem and asthma as a lung problem. The evidence has been quietly dismantling that division for two decades.

The atopic march

The atopic march describes a pattern in which eczema and food allergy in infancy are followed, in a meaningful proportion of children, by allergic rhinitis and asthma later on. In one Canadian birth cohort, children with eczema and sensitisation at age one had roughly eleven-fold and seven-fold increases in asthma and rhinitis respectively by age three.²⁷ In a Thai cohort of children diagnosed with eczema at eighteen months, 61.8 per cent went on to develop allergic rhinitis and 29.4 per cent developed asthma.²⁷

The proposed mechanism is called transcutaneous sensitisation — the idea that when the skin barrier is compromised, allergens entering through it teach the immune system to react to them, and that lesson is then applied everywhere, including in the lungs. Mutations in filaggrin, a protein central to barrier integrity, are associated with both higher food sensitisation and a greater likelihood of developing asthma after eczema.²⁷

In Australia, around 2.8 million people — 11 per cent of the population — were living with asthma in 2022. Among children it is more common in boys; among adults it is more common in women.²⁸ South Australia has historically carried a high burden.

These are not childhood conditions people age out of

The phrase “atopic march” does real damage here, because it sounds like a procession that ends. It is worth saying clearly that it often does not.

• Roughly 7 per cent of adults have atopic dermatitis, and about one in four adults with it report that it began in adulthood — not in childhood at all.⁴² Adult atopic dermatitis also tends to differ from the childhood form in where it appears and what it looks like, which is part of why it goes unrecognised.⁴²
• The Australian prevalence figure above is a whole-population figure, and adult women carry more of it than adult men.²⁸
• Cold urticaria. Most often first appears in young adults rather than children, occurs at any age, and shows a clear female predominance.^43,44

So while the research literature leans heavily on childhood cohorts — because birth cohorts are how you study a march — the conditions themselves are lifelong propositions for a great many people. Everything in this article about weather, pollen and skin applies at 46 as much as at 6.

But it is not a neat parade

Honesty check, because the atopic march is often presented as an inevitability, which is both wrong and frightening for parents. In one analysis only 3.1 per cent of children followed the classical sequence, with over 90 per cent of atopic children showing non-sequential patterns — and some cohorts even describe a “reverse” march where asthma precedes eczema.²⁷

So the useful framing is not “eczema leads to asthma.” It is that eczema, food allergy, hay fever and asthma are expressions of a shared underlying susceptibility, of which barrier function is one important part. Having one raises the likelihood of another. It does not sentence anybody to anything.

What it does mean is that on a high-pollen day, a person with reactive skin and a person with asthma are not two different people having two different problems. Very often they are the same person, having one.

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The Anaphylaxis Thread

This section needs a careful hand, because anaphylaxis is serious and the last thing anyone needs is to be frightened about the weather. So, plainly first: no skincare product treats, prevents or affects anaphylaxis in any way, and nothing in this section should change how anyone manages a known allergy. That belongs to your doctor, your allergy specialist, and an ASCIA Action Plan.

But there is a real and quite recently measured connection between airborne pollen and food allergy reactions, and people living with both deserve to know it exists.

Pollen and food are talking to each other

Pollen-food allergy syndrome — also called oral allergy syndrome — happens when the immune system, primed to a pollen protein, encounters a structurally similar protein in a raw fruit, vegetable, nut or seed and reacts to it. It affects roughly 5 to 8 per cent of the general population, but up to 50 to 70 per cent of people who are sensitised to pollen.²⁹

Most of it is mild and confined to the mouth — itching, tingling, slight swelling — and many of the culprit proteins are destroyed by heat, which is why a cooked apple is often fine when a raw one is not. But systemic reactions occur in an estimated 2 to 10 per cent of cases, and severe outcomes in around 1 to 2 per cent.²⁹ Small percentages, but not zero.

The Melbourne finding that ties it all together

This is, to my mind, the most striking piece of research in this whole article, and it is Australian.

Researchers followed children in the Melbourne HealthNuts cohort — 1,108 infants assessed at age one, 675 of whom had data again at age six — and matched their allergy testing to the actual daily grass pollen count on the day of testing and the days preceding it.³⁰ Per 20 grains per cubic metre rise in pollen, what they found was:

• In six-year-olds, cumulative grass pollen exposure was associated with up to 1.2-fold increased odds of skin-prick test reactivity to peanut, cashew, hazelnut, almond, egg and sesame.
• In the same children, cumulative pollen exposure was associated with a 13-fold increase in eczema flares.
• And in peanut-allergic one-year-olds undergoing supervised oral food challenges, higher pollen concentrations were associated with reacting at a lower dose.

Read that last one again. On high grass pollen days, the amount of peanut required to provoke a reaction went down. The authors conclude that persistent grass pollen exposure may trigger a dysregulation of immune responses that raises both food test reactivity and eczema flares.³⁰

The pollen in the air appears to change how much of a food it takes to cause a reaction. Skin, gut and airway are not running separate accounts.

Cofactors: the threshold moves

This connects to something allergy specialists have understood for a while. Many food-allergic reactions are not simple on-off switches but threshold events, and a set of cofactors can lower that threshold on a given day.

In food-dependent exercise-induced anaphylaxis, a person tolerates the food alone and the exercise alone, but the combination causes a reaction. The recognised cofactors are exercise first and foremost, then anti-inflammatory medications and alcohol, with physical stress, infection, menstruation, high temperature and humidity also implicated.³¹ In one series, 75 per cent of wheat-dependent cases required a cofactor to react at all; adding aspirin to exercise reduced the tolerated food threshold by 87 per cent.³¹

And pollen appears to belong on that list. In a study of anaphylaxis in pollen-sensitised children, 63.6 per cent of the exercise-induced episodes occurred during pollen season.³²

So a hot day, in pollen season, with exercise, is not one risk factor. It is three, stacking.

Does the same thing happen with cold urticaria?

It is a fair question to ask, and worth asking, because cold urticaria is another condition where hives can escalate to anaphylaxis and where mast cells and histamine are doing the damage. If pollen can lower the threshold for a food reaction, does it lower the threshold for a cold reaction too?

On the current evidence, no — not in the same way. And the reason is worth understanding, because it clarifies what a cofactor actually is and is not.

Why the two conditions diverge

A food-allergic reaction is IgE-mediated against a specific protein. The immune system is already primed to that protein, and something that raises overall immune activation can plausibly tip a borderline dose over the line — which is what the threshold research describes.

Cold urticaria is a chronic inducible urticaria. The trigger is a physical stimulus — cold itself — rather than an allergen the immune system has learned to recognise. Mast cells and histamine do the damage in both cases, but what pulls the trigger is different.

And the recognised aggravating factors for chronic urticaria reflect that. They are anti-inflammatory medications and aspirin, heat, tight clothing and hot showers, emotional stress, fatigue and poor sleep, and intercurrent infections. Inhalant allergens and pollen do not appear on that list.³⁷ Atopic conditions — allergic rhinitis, asthma, eczema — are more common in people with chronic urticaria than in the general population, but the evidence indicates they do not drive the disease itself.³⁷ One review of cold anaphylaxis concluded specifically that atopic comorbidity “seems not to be highly associated” with it.³⁸

What does raise the risk in cold urticaria

An entirely different list: a previous systemic reaction to a bee or wasp sting, angioedema, throat or oropharyngeal symptoms, itchy earlobes, asthma as a comorbidity, a strongly positive cold stimulation test, and raised blood eosinophils.³⁸

Cold anaphylaxis affects a genuine minority of people with cold urticaria — reported rates range from 0 to 34.3 per cent depending on the population studied, with roughly 21 per cent commonly cited and 17.3 per cent in one paediatric series.^37,38

Who actually has this

Before the triggers, the demographics, because cold urticaria is routinely miscast as a childhood curiosity. It affects around 0.05 per cent of the population in central European data, occurs at any age, most often first appears in young adults rather than children, and has a clear female predominance.^43,44 Typical disease duration is around 6.3 years, and while people do recover spontaneously, “a few years” is not the same as “by the time they grow up.”⁴³

And across all ages, 10 to 38 per cent of people with cold urticaria have had at least one severe systemic reaction involving low blood pressure or its symptoms.⁴³ That is not a rare complication of a minor condition. It is a substantial minority of everyone who has it.

Two questions that get confused — and shouldn’t be

There is a distinction here that is easy to blur, and blurring it does real harm, so it is worth separating carefully. What triggers a reaction and what triggers the most severe reactions are two different questions with two different answers.

The clearest trigger breakdown comes from a paediatric series, so read the proportions as indicative rather than universal — but they are stark. The exposures that provoked cold urticaria symptoms were cold water in 95.2 per cent, cold air in 66.7 per cent, ingesting something cold in 19 per cent, and contact with cold surfaces in 14.3 per cent. Most — 71.4 per cent — reacted to more than one of these.³⁸ Adult guidance lists the same everyday exposures: cold air and sudden drops in air temperature, cold water, cold food and drink, cold objects, and air-conditioned rooms, with damp and windy conditions intensifying symptoms.^43,44

So cold air is not a minor trigger. It is a trigger for around two people in three.

What is true is that when reactions escalate, whole-body cold water immersion is disproportionately responsible. In that paediatric series, 90.5 per cent of anaphylactic episodes followed complete immersion, against 9.5 per cent after cold-air exposure;³⁸ the French management guideline puts water immersion behind up to 77 per cent of severe systemic reactions across all ages.⁴³ The likely reason is simple physics — immersion drops the temperature of a very large area of skin at once, so far more mast cells are triggered simultaneously than a cold wind on a face and hands can manage.

But that residual fraction is not zero. Cold air caused anaphylaxis in two of the twenty-one children in that series, and around a quarter of severe systemic reactions in the adult-inclusive guideline figure arise from something other than immersion.^38,43 Anyone told that cold air is the “safe” trigger has been told something the evidence does not support.

Winter is absolutely its own weather season

Everything earlier in this article is about spring and early summer. For a household living with cold urticaria, the difficult months are the opposite ones, and the mechanisms are just as weather-driven.

• Cold air and wind chill. Ambient cold is one of the most commonly reported triggers, and wind matters because it strips warmth from exposed skin faster than still air of the same temperature. Face, ears, hands and wrists are the usual sites, for the same reason they are the usual sites in the pollen story — they are what is uncovered.^38,40
• Rewarming is when it shows. This catches people out constantly. The hives typically appear not during the cold exposure but as the skin warms again afterwards.^37,40 Which means the reaction often arrives after coming indoors, in front of a heater, when everyone has relaxed and assumed the risk has passed.
• Winter infections. Intercurrent viral and bacterial infections are a recognised aggravator of chronic urticaria.³⁷ Winter is when households collect them. This is a genuine seasonal cofactor — arguably the closest true equivalent, for cold urticaria, of what pollen season appears to be for food reactions.
• The everyday cost is not trivial. In interviews with adults, adolescents and children, winter was consistently described as intensifying symptom frequency. People reported dressing conspicuously differently from everyone around them, giving up swimming, skiing and outdoor activities, keeping medication at school or work, and living with frustration, worry and low mood about the restrictions.⁴⁰

So there are two weather seasons in this article, not one. They run on opposite logic, and a household can easily be managing both.

“Will it go away?” — the honest answer

This is the question everyone asks, whether about themselves or about someone they care for, and the honest answer is neither bleak nor falsely cheerful.

In an Australian follow-up study of 99 patients seen in the ACT, resolution rates were about 17.9 per cent at five years and 24.5 per cent at ten. By the end of follow-up 22 per cent had complete resolution and a further 23 per cent had improved — but 55 per cent were stable or worse. Coexisting allergic conditions and a longer symptom history at first assessment both predicted persistence.⁴¹

So: it can settle, roughly a quarter of people are clear within a decade, and the rest are not. “They’ll grow out of it” is a reasonable hope and a poor plan. Anyone still reacting in adulthood is not an unusual case — they are, on these numbers, the majority.

That also means adult management deserves to be active rather than resigned. Current guidance runs a clear ladder: second-generation antihistamines at standard dose first, increasing up to four times the standard dose if needed, then adding omalizumab. An adrenaline autoinjector is recommended for anyone with a documented history of anaphylaxis to cold or of throat or laryngeal involvement.⁴³ If someone has been managing on avoidance alone for years because nobody revisited it after childhood, that is worth raising with a clinical immunologist.

Two real connections that do exist

1. Asthma is the bridge. Asthma comorbidity is a recognised risk factor for cold anaphylaxis.³⁸ Pollen season worsens asthma. So a heavy spring could plausibly matter for someone living with both — not by changing how their skin responds to cold, but by degrading their asthma control underneath it. That is an indirect and, as far as I can find, untested route. Worth naming as a hypothesis, not a finding.
2. Ozone, not pollen. In a prospective cohort of 161 people with chronic urticaria — spontaneous and inducible both — disease control was measurably worse in summer, and the one environmental factor consistently associated with that was ozone, not particulates or traffic pollution.³⁹ Ozone climbs on hot, still, sunny days: exactly the days this article has been describing. So there is a real weather link to urticaria. It simply is not a pollen link.

The threshold model is real in both conditions. It is the list of things that move the threshold that turns out to be different.

Two seasons to plan for

In South Australia this produces a genuinely awkward calendar. Winter and its cold winds are the long stretch to manage. But the sharpest single risk often sits in summer — a swim in water considerably colder than the air, then getting out into a breeze and rewarming. Cold water is the highest-severity exposure, and it does not require a cold day to be dangerously cold.

So a household with both hay fever and cold urticaria is managing two weather seasons that run on opposite logic, plus a summer water risk sitting inside the warm one. That is genuinely difficult to hold in your head, and anyone finding it hard is not being disorganised. It is hard.

If cold urticaria is part of your life, we have written about it in much more depth in Cold Comfort: Understanding Cold Urticaria — including the point that matters most, which is never to swim alone.

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What Actually Helps

Framed for skin and for everyday comfort, and staying strictly within what the evidence supports.

Timing and exposure

Getting it off once it has landed

This is ASCIA’s own advice, not something invented for a skincare article: shower after outdoor exposure, keep windows closed on high-pollen and windy days, wear sunglasses, use recirculated air in the car, and wear a mask if you are mowing.⁴

The showering point is the one that matters most for skin, and it has a simple logic: whole pollen grains land and stay. Rinsing them off before they spend the night against your face — and off the pillowcase — removes the source rather than treating the response.

On how to do that rinsing: in children with controlled eczema during summer, water-only cleansing was as effective as soap or detergent.²⁰ Gentle is not a compromise here. Stripping a barrier that is already under four kinds of pressure is working against yourself.

Indoor humidity — and a genuine tension

Sustained indoor relative humidity below roughly 40 to 50 per cent suppresses house dust mites, whose allergen levels rise substantially as humidity rises.³³ But abrupt drops in humidity disturb the skin barrier.¹⁹ These two facts pull in opposite directions, and anyone who gives you a single magic number is oversimplifying. The workable version is: avoid damp, avoid sudden swings, and don’t run a dehumidifier or heater so hard that the air becomes a desert.

Before the season, not during it

For anyone with hay fever, the National Asthma Council’s guidance is to start preventive treatment at least two weeks before the high-pollen period rather than reacting once symptoms arrive.¹³ Given the Adelaide grass season effectively runs October to December, that puts the conversation with your GP in September.

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Where the Science Is Still Thin

A short list, because knowing what we don’t know is part of knowing anything.

1. Nobody has measured how much pollen actually deposits on human skin in real-world conditions, or what dose produces a flare. The airway dose-response work has no skin equivalent.
2. Sub-pollen particles and skin. Everything known about those 600-nanometre fragments concerns the lower airways. Whether they matter more or less than whole grains for skin is simply unstudied.
3. The thunderstorm rupture mechanism is unresolved, and the most-cited explanation does not fit the worst recorded event.⁵
4. South Australian data are sparse — one pollen monitoring location for the whole state in the 2025 analysis, and pollen count did not mediate the storm–asthma association here.²⁵
5. Wind effects on skin are essentially unquantified, despite wind obviously increasing both deposition and water loss.
6. Climate effects on eczema are regionally inconsistent, and findings from northern-hemisphere cohorts cannot simply be transplanted to a Mediterranean-climate Australian city.²⁰
7. Nobody appears to have directly tested whether pollen season shifts cold urticaria thresholds. The answer given above is drawn from what the recognised aggravating factors are and are not, rather than from a study that set out to measure it. That is an absence of evidence rather than evidence of absence, and it is a reasonable question for someone to put to their immunologist.

⁂

Adelaide Notes

When the season runs

Why our geography does this to us

Adelaide sits between grassland plains and the Mount Lofty Ranges, in a Mediterranean climate of wet cool winters and hot dry summers, with a spring that alternates between hot northerlies and cool gulf south-westerlies. That alternation is the entire story in miniature — one wind brings continental air across grassland, the other brings maritime air off the water. And the SA thunderstorm asthma study named the Adelaide Metropolitan and Hills region specifically.²⁵ For those of us in the Hills, that is not an abstract finding.

Keeping an eye on it

The Adelaide Pollen Count has run as a partnership between Asthma Australia, the University of Adelaide and the AusPollen network, using a Burkard trap with manual microscopy and reporting on a Low / Medium / High / Extreme scale through the season.³⁴ Daily pollen and air quality tracking is also available through the AirRater app, which has covered South Australia since 2019.³⁵

One caveat worth stating: monitoring arrangements in Adelaide have shifted in recent years, and the service running any given season is worth checking rather than assuming. If you rely on the count, confirm which service is operating before the season starts.

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The Thread That Runs Through All of It

What stays with me, having gone through this research, is how thoroughly the boundaries we draw between these conditions dissolve when you look at the mechanisms.

The same ryegrass pollen that settles on a cheekbone and picks at a barrier with its enzymes is, a few kilometres up and a few hours later, the thing that ruptures in a storm and fills an emergency department. The same day’s pollen count that predicts an eczema flare in a six-year-old also predicts how much peanut it will take to provoke a reaction in a one-year-old. The barrier that lets an allergen into the skin is part of how the immune system learns to react to it in the lungs.

It is one system, meeting one atmosphere, on one afternoon.

Which is, I think, quietly reassuring rather than alarming. It means the unglamorous things — knowing which way the wind is blowing, closing up before the storm rather than after, rinsing off what has landed, being gentle with a barrier that is already busy, and having the conversation with your GP in September rather than November — are not trivial. They are working on the actual mechanism, at the actual point where it starts.

And it means that if you have spent years being told your symptoms don’t make sense — that pollen shouldn’t affect your skin, that you shouldn’t feel worse at night, that rain should have helped — the research is, on nearly every count, on your side.

Sources

1. On the causes of variability in amounts of airborne grass pollen in Melbourne, Australia. International Journal of Biometeorology, 2011. link.springer.com/article/10.1007/s00484-010-0361-x
2. Asthma Australia. Wet winter sets up a higher pollen season for Adelaide, 2025. asthma.org.au
3. Medium-term increases in ambient grass pollen in Brisbane, Australia. Frontiers in Allergy, 2021. frontiersin.org
4. ASCIA. Pollen Allergy — Frequently Asked Questions, 2024. allergy.org.au
5. Emmerson KM et al. Atmospheric modelling of grass pollen rupturing mechanisms for thunderstorm asthma prediction. PLOS One, 2021. journals.plos.org
6. Climate change and thunderstorm asthma in children: challenges and responses. World Journal of Pediatrics, 2025. link.springer.com/article/10.1007/s12519-025-01012-3
7. Interaction between Air Pollutants and Pollen Grains: Effects on Public and Occupational Health. Atmosphere, 2023. mdpi.com/2073-4433/14/10/1544
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11. Atmospheric transport reveals grass pollen dispersion distances. Science of the Total Environment, 2022. eprints.worc.ac.uk
12. Changes in concentration of Alternaria and Cladosporium spores during summer storms. International Journal of Biometeorology. link.springer.com/article/10.1007/s00484-012-0604-0
13. National Asthma Council Australia. Thunderstorm Asthma information paper, 2022. nationalasthma.org.au
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17. Ritsick DR, Lambeth JD. Spring brings breezes, wheezes, and pollen oxidases. Journal of Clinical Investigation, 2005 — commentary on Boldogh I et al., on reactive oxygen species generated by pollen NADPH oxidase. jci.org/articles/view/26023
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31. Food-Dependent Exercise-Induced Anaphylaxis: A Distinct Form of Food Allergy — An Updated Review. Foods, 2023. mdpi.com/2304-8158/12/20/3768
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35. AirRater. What does it monitor. airrater.org
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40. A qualitative interview study exploring the lived experiences of adults, adolescents, and children with chronic inducible cold urticaria. Journal of Patient-Reported Outcomes, 2025. link.springer.com/article/10.1186/s41687-025-00970-6
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