Spring has barely begun, yet the signs are already unmistakable: the yellow dust on cars, the stinging eyes, the relentless sneezing. This year’s pollen season is predicted to be worse than usual, driven by a warm spring that has pushed trees into early flowering – and the evidence is mounting that climate change is making these seasons longer, more intense, and harder to escape.
For the millions of people in the UK who suffer from hay fever, the misery is arriving earlier and staying longer. The Met Office, which provides daily pollen forecasts across the country, has already recorded unusual pollen bursts in 2026. A long wet spell followed by a sudden warm snap in late February triggered an exceptionally early and intense release of alder and hazel pollen, with counts in London hitting “very high” before March had even begun. Birch season, typically a key culprit for tree-pollen allergies, began about ten days ahead of the long-term average.
The problem: a season that keeps expanding
Seasonal allergies – medically known as allergic rhinitis or allergic conjunctivitis – affect more than one in four adults in the United States, and the situation in the UK is similarly widespread. Allergy UK reports that individuals are experiencing more severe and longer-lasting symptoms, affecting their quality of life, concentration, sleep, and even school performance during exam periods. Poorly controlled hay fever can also exacerbate asthma and eczema.
The core driver of these symptoms is a protein found in pollen. Pollen is the male reproductive material plants release to fertilise others, but when the human immune system develops an allergic antibody – IgE – to these proteins, trouble begins. When several IgE molecules bind to the allergen as it lands on the tissues of the eye or nasal passages, cells release histamine, prostaglandins and leukotrienes. These molecules interact with blood vessels and nerves, triggering the itchy, watery eyes, runny nose, sneezing, congestion and nasal itching that allergy sufferers know all too well.
Pollen seasons follow a predictable pattern in the UK. Tree pollen comes first, typically from late March to mid-May, with hazel and alder sometimes appearing as early as January or February. Ash, birch – often the most problematic – oak and plane trees follow. Grass pollen, affecting around 95 per cent of hay fever sufferers, runs from mid-May to July, with two peaks in early June and early July. Weed pollen, including nettle and dock, appears from late June to September, peaking in July and August. But these windows are shifting.
How climate change reshapes pollen seasons
The single most important factor driving worse pollen years is climate change. Rising global temperatures and higher levels of atmospheric carbon dioxide, largely from burning fossil fuels, are directly lengthening and intensifying pollen seasons across the UK and mainland Europe. A Lancet Countdown report indicates that pollen seasons have already extended by one to two weeks since the 1990s.
Warmer temperatures cause plants to emerge from dormancy earlier. Once temperatures rise above about 4°C (40°F), trees begin waking up. The unprecedented warm spring of 2026 in much of the United States – and similar conditions in the UK – has driven early tree-pollen emergence. In some locations in North America, the growing season is now two weeks longer on average than in the 1990s, and more than four weeks longer than in the 1970s. The same pattern holds true for the UK: researchers have found that tree pollen seasons for birch, alder and olive began one to two weeks earlier between 2015 and 2024 compared with the period 1991 to 2000. Mild winters can even lead to pollen releases as early as January or February.
But length is not the only change. Higher carbon dioxide levels increase plant growth, leading to longer pollination periods and more pollen produced by each plant. With higher pollen counts, more people develop symptoms – and allergists report seeing an increasing number of patients who are experiencing allergies for the first time.
Beyond quantity, climate change may also alter the potency of pollen. A single pollen particle can carry varying amounts of allergy-causing agents. Studies show that the seasonal severity of birch and alder pollen has increased by 15 to 20 per cent in parts of the UK, particularly in the south, as well as in northern France and Germany.
Weather conditions on a day-to-day basis interact with these longer-term trends. Windy days blow pollen over wider areas. Rain can temporarily scrub pollen from the air, but humidity and moisture after rain cause pollen granules to rupture, making them easier to carry on the wind and breathe in – this is especially true for grass pollen. In the UK, April 2026 has been warm and wet in many parts of England and Wales. If May and June turn dry, a sharp grass-pollen spike is anticipated as the abundant growth dries out and releases pollen simultaneously.
Air pollution adds another layer. Pollutants from vehicles, particularly particulate matter (PM2.5) and ozone, can interact with pollen grains, making them more allergenic and increasing their ability to penetrate the respiratory tract. This interaction worsens symptoms for allergy sufferers, and outdoor air pollutants tend to peak in the midday and afternoon heat.
There is also a threat from invasive species. Climate change is making conditions more favourable for plants like common ragweed (Ambrosia), which is on the watch list in Europe and is projected to become a common health problem across the continent.
What can be done: managing symptoms and exposure
For those already suffering, there are practical steps to reduce exposure and alleviate symptoms. The first line of defence is avoidance. Keeping windows closed during the pollen season reduces the amount of allergens entering the home. Wiping down pets with a damp towel removes pollen they carry indoors. Avoiding clotheslines when pollen counts are high prevents allergens from settling on washed items. Changing clothes or showering after being outdoors reduces the amount of allergens that remain on the body.
Using HEPA air purification in the home can lower household allergen levels, but experts advise choosing non-ionising filters because ionising air filters can generate ozone, which worsens indoor air quality. Other useful measures include vacuuming regularly with a HEPA filter, dusting with a damp cloth, washing hair before sleeping, avoiding walking on grass in the early morning and evening when pollen counts are highest, and using pollen filters in car vents. Checking the pollen forecast from the Met Office – which now uses a new model for five-day predictions across the UK – can help people plan their days. Pollen counts are generally highest in the morning.
When avoidance is not enough, medications can help. A saline nasal rinse reduces mucus and allergens inside the nasal passages. For mild symptoms, daily non-sedating (second-generation) antihistamines can be effective. For moderate to severe allergies, daily use of nasal steroids can bring relief, though they can take several weeks to reach peak effect. A nasal antihistamine spray can provide additional benefits. Antihistamine eye drops are also useful. In dry conditions, nasal hydration sprays like saline can ease congestion.
If medications fail, immunotherapy – available as allergy shots or under-the-tongue tablets – offers a longer-term solution. Subcutaneous immunotherapy (SCIT) involves injections under the skin, typically for hay fever, house dust mite, animal dander and insect venom allergies, and requires a build-up and maintenance phase of three to five years. Sublingual immunotherapy (SLIT) uses tablets or drops placed under the tongue daily, available for grass and tree pollen allergies, house dust mite, and some animal dander allergies. The National Institute for Health and Care Excellence (NICE) has recommended an under-the-tongue tablet for birch pollen allergy, potentially benefiting up to 27,000 people in England. However, immunotherapy carries side effects such as local site reactions and asthma symptoms, and may rarely trigger a severe allergic reaction known as anaphylaxis.
New developments are also on the horizon. A needle-free nasal spray alternative to adrenaline auto-injectors for severe allergic reactions – called Neffy – has been developed, and a potential preventative vaccine for peanut allergy is being trialled.
Broader implications and the scale of the challenge
The rise in allergies is not just a seasonal nuisance; it is a major public health concern. Projections indicate that by 2026, one in three people in the UK could be living with an allergy, potentially rising to one in two. The economic burden of allergic disease in the European Union alone is estimated at up to €151 billion.
Organisations such as Allergy UK, the NHS, Asthma + Lung UK, and the Met Office provide guidance and resources. Asthma + Lung UK warns that high pollen levels can be dangerous for people with asthma and other lung conditions, potentially triggering life-threatening reactions. Pollen-monitoring schemes, including the UK Pollinator Monitoring Scheme (PoMS), track changes in pollinating insects, which are vital for ecosystems and agriculture – changes in their populations can have wider environmental implications.
For now, the immediate forecast is clear: a warm spring has set the stage for an intense pollen season, and the underlying trends driven by climate change mean that this is unlikely to be an isolated bad year. Understanding what is causing the symptoms – and finding the right solutions – can help sufferers cope, even in a year when the pollen counts are higher than ever.