One continuous airway, one inflammation. Why pollen season shows up in asthma admissions, what a thunderstorm does, and why the nasal spray is part of asthma treatment.
Part of the Complete Hay Fever Guide.
Key fact: Untreated hay fever makes asthma harder to control, and treating the nose properly measurably improves the chest. The nose and the lungs are one airway with one continuous lining — which is why pollen season shows up in asthma admissions every June.
One airway, not two
The lining of the nose and the lining of the bronchi are continuous, structurally similar and populated by the same inflammatory cells. Allergic inflammation does not respect the boundary between them. This is why the two conditions travel together: the large majority of people with asthma also have allergic rhinitis, rhinitis frequently appears first and predicts who will go on to develop asthma, and the severity of one tends to track the severity of the other.
Treating them as two unrelated problems — a tablet for the nose from one shelf, an inhaler for the chest from a different clinic — is the mistake this guide exists to correct. If your hay fever is uncontrolled, your asthma is being made harder to control, and no amount of reliever inhaler addresses that.
What pollen season does to asthma
The effect is measurable and predictable. Across the UK, asthma exacerbations, unscheduled appointments and hospital admissions all rise through the grass pollen season, and the rise tracks the pollen count. At an individual level, the pattern people describe is a summer in which the reliever inhaler is needed more often, exercise is harder, and sleep is broken by coughing — usually attributed to the heat rather than to the pollen.
~80%
Of people with asthma also have allergic rhinitis
Jun–Jul
When UK asthma attacks driven by grass pollen peak
2 wks
Head start a nasal spray needs to be working by the peak
The UK pollen and spore seasons
Which months are hardest depends on what you are allergic to. As a general guide:
| When | Main allergen | What it means for asthma |
|---|---|---|
| Late March to May | Tree pollen (birch, ash, oak) | A trigger for people allergic to tree pollen |
| May to July | Grass pollen | The main UK hay fever season, and when pollen-related asthma flares are most common |
| June to September | Weed pollen | A smaller late-summer season for some people |
| Late summer into autumn | Mould spores, such as Alternaria and Cladosporium | Sensitivity to Alternaria in particular has been linked with severe asthma attacks |
The UK pollen calendar has the detail, and our guide to autumn asthma covers the spore season.
The mouth-breathing problem
There is a mechanical reason a blocked nose matters to the chest, quite apart from the shared inflammation. The nose warms, humidifies and filters inhaled air. When it is blocked and breathing shifts to the mouth, air arrives at the lower airway colder, drier and carrying more of what was in it. Cold, dry air is itself a bronchoconstrictor in asthma, which is why exercise on a cold day is a classic trigger.
So a blocked nose in June delivers unfiltered pollen-laden air straight to an airway that is already inflamed, all night, every night. Unblocking the nose is not a comfort measure in that situation. It changes what the lungs are breathing.
Other ways the nose affects the chest
Mouth breathing is not the only link. Two others are thought to play a part:
- Post-nasal drip. Mucus and inflammatory secretions from the nose run down the back of the throat and can irritate the airways below, which is one reason hay fever brings on a cough.
- A shared allergic response. When an allergen such as pollen is breathed in, the immune system releases histamine and other chemicals in the lining of the nose and the lungs at the same time, and allergic inflammation in the nose is thought to make the airways lower down more reactive.
The practical message is the same: hay fever that is left untreated keeps the whole airway inflamed. For other things that set off asthma, see our guide to asthma triggers.
Thunderstorm asthma
Intact grass pollen grains are too large to reach the small airways; they are filtered out higher up, which is why grass pollen usually causes nose and eye symptoms rather than chest ones. A thunderstorm changes that. The humid downdraught ahead of a storm draws pollen grains down to ground level and ruptures them osmotically into far smaller fragments, which are small enough to be inhaled deep into the lung in very large numbers.
If you have both hay fever and asthma, take a thunderstorm in pollen season seriously. Episodes of mass presentation to emergency departments within hours of a summer storm are well documented, including in people whose asthma is normally mild and in some who did not know they had asthma. Keep your reliever inhaler with you, stay indoors with the windows shut while the storm passes, and do not wait to see whether it settles.
Why treating the nose helps the chest
This is the part that changes what people do. Treating allergic rhinitis properly — specifically, with a regularly used steroid nasal spray rather than an antihistamine alone — is associated with better asthma symptom control, less reliever use and a lower risk of asthma exacerbations and emergency attendances.
The reasons are the ones already described: less shared inflammation, and nasal breathing restored so that air reaching the chest is warmed, humidified and filtered. The practical implication is simple. If you have asthma and hay fever, a steroid nasal spray is not an optional extra for comfort. It is part of your asthma management.
| Treatment | Effect on the nose | Effect on asthma |
|---|---|---|
| Steroid nasal spray — fluticasone furoate, fluticasone propionate, beclometasone, budesonide | The most effective treatment for blockage and the underlying inflammation | Associated with better symptom control and fewer exacerbations |
| Daily non-drowsy antihistamine | Sneezing, itching, runny nose, itchy eyes | Helpful for the nasal symptoms; not a treatment for asthma in itself |
| Preventer inhaler | None | The foundation of asthma control — and the thing most often quietly dropped over summer |
| Reliever inhaler | None | Rescue only. Needing it more often is information, not a solution |
Antihistamines and asthma
Non-drowsy antihistamines such as cetirizine, loratadine and fexofenadine are safe to take alongside asthma inhalers. They work well for sneezing, itching, a runny nose and itchy eyes, but do little for a blocked nose, and they are not a treatment for asthma. Older, drowsy antihistamines such as chlorphenamine are generally not the first choice for regular daily use because of drowsiness. If your hay fever is more than mild, a steroid nasal spray used every day does more for the nose, and for the chest, than an antihistamine alone.
Montelukast: one tablet for both
Montelukast is a daily tablet called a leukotriene receptor antagonist. Leukotrienes are chemicals that narrow the airways and inflame the lining of the nose, and montelukast blocks them. In the UK it is licensed as an add-on treatment for asthma and, in people who have asthma, for relief of seasonal hay fever symptoms.
It is not a first treatment. The 2024 NICE, BTS and SIGN asthma guideline starts adults and young people on an inhaled steroid with formoterol (AIR or MART). If asthma is still not controlled on a moderate dose, a doctor may check inflammation markers and then refer to a specialist or try an add-on such as montelukast for 8 to 12 weeks, stopping it if it does not help. Our guide to add-on asthma treatments explains the options.
MHRA safety warning: montelukast can cause changes in mood, behaviour and sleep, including nightmares, agitation, depression and, rarely, suicidal thoughts. These have been reported in adults and children. Tell your prescriber straight away if you or your child notice any of these.
Allergen immunotherapy
Allergen immunotherapy (desensitisation) gives regular, gradually increasing doses of the allergen, as injections or as tablets or drops under the tongue, usually over about three years. It is the only treatment that changes the allergy itself rather than just easing symptoms, and in people with hay fever it may also reduce asthma symptoms. In the UK it is given by specialist allergy services, for people whose hay fever is not controlled by nasal sprays and antihistamines. Asthma must be well controlled before starting, because poorly controlled asthma raises the risk of a reaction. Ask your GP about referral if standard treatment is not enough.
What to do through the season
- Keep the preventer going. Summer is exactly the wrong time to let a preventer inhaler slide, and it is the time people most often do, because the winter viruses have stopped.
- Start a steroid nasal spray two weeks before your season — early May for grass pollen. The UK pollen calendar sets out when each season runs.
- Add a daily antihistamine for the sneezing, itching and eye symptoms.
- Carry the reliever, particularly on high-count days and in unsettled weather.
- Check inhaler technique at the start of the season rather than in the middle of a bad week.
- Have a written asthma action plan and know what it says to do when symptoms step up.
- Treat rising reliever use as a warning. Needing it three or more times a week means the asthma is not controlled, whatever the reason.
- Check the pollen forecast each day on the Met Office, and plan outdoor time for lower-count days.
- Keep pollen out of the house. Keep windows closed in the early morning and evening when counts are higher, shower and change your clothes after time outdoors, and dry washing indoors on high-count days.
- Wear wraparound sunglasses to keep pollen out of your eyes.
- Avoid cutting grass, or being nearby while it is cut.
- Check your prescriptions are up to date before the season starts, so you do not run short of your preventer, reliever or nasal spray.
When to get help urgently
Call 999 if the reliever inhaler is not helping or not lasting four hours, if you are too breathless to speak in full sentences, eat or sleep, if breathing is fast and it feels like you cannot get enough air, or if lips or fingers look blue. Do not drive yourself.
Arrange a review, without waiting for the season to end, if you are using your reliever three or more times a week, waking at night with cough or wheeze, finding your usual activity limited, or have needed a course of steroid tablets for asthma in the past year.
Frequently Asked Questions
Can hay fever make asthma worse?
Yes, and the effect is well established. Asthma exacerbations and hospital admissions rise across the grass pollen season, and people with both conditions typically need their reliever inhaler more often through the summer. The nose and the lower airway share one continuous lining and the same allergic inflammation, so uncontrolled rhinitis makes asthma harder to control.
Does treating hay fever improve asthma?
Treating allergic rhinitis with a regularly used steroid nasal spray is associated with better asthma symptom control, less reliever use and fewer exacerbations. Two things appear to be at work: less shared inflammation across the airway, and restored nasal breathing, so air reaching the chest is warmed, humidified and filtered rather than arriving cold, dry and unfiltered through the mouth.
What is thunderstorm asthma?
A sudden surge of asthma attacks during or shortly after a summer thunderstorm. Humid downdraughts pull pollen to ground level and burst the grains into fragments small enough to be inhaled deep into the lungs, where whole grains would normally be filtered out by the nose. It can affect people whose asthma is usually mild. If you have hay fever and asthma, keep your reliever with you and stay indoors with windows shut while a storm passes.
Should I keep using my preventer inhaler in summer?
Yes. Summer is when preventer inhalers are most often quietly dropped, because the winter viral triggers have gone, and it coincides exactly with the pollen peak. If anything, pollen season is a reason to be more consistent with a preventer, not less. Any change to preventer treatment should be a decision made with a clinician, not a drift.
I only wheeze in summer. Is that asthma?
It may well be. Seasonal wheeze, cough or chest tightness alongside hay fever is a recognised pattern and it deserves proper assessment rather than being managed with hay fever medicines alone. Antihistamines and nasal sprays do not treat the lower airway. Speak to a clinician about whether you need testing and an inhaler.
Can hay fever cause asthma?
Hay fever doesn’t directly cause asthma, but the two are closely linked. People with hay fever are more likely to develop asthma, hay fever often comes first, and both are driven by the same allergic inflammation in one continuous airway. If you get a cough, wheeze or chest tightness with your hay fever, see your GP or asthma nurse to check whether you have asthma, rather than treating it with hay fever medicines alone.
What is united airway disease?
United airway disease is the idea that the nose and sinuses (the upper airway) and the bronchi and lungs (the lower airway) are one continuous airway, lined by the same tissue and affected by the same allergic inflammation. It explains why hay fever and asthma so often occur together, why uncontrolled hay fever makes asthma harder to control, and why treating the nose properly helps the chest.
Can montelukast treat both asthma and hay fever?
Yes, in some people. Montelukast is a daily tablet licensed in the UK as an add-on treatment for asthma and, in people with asthma, for relief of seasonal hay fever symptoms. It is not a first treatment: under the 2024 NICE, BTS and SIGN guideline it may be tried for 8 to 12 weeks if asthma is not controlled on an inhaled steroid and formoterol inhaler. The MHRA warns it can cause changes in mood, behaviour and sleep, so tell your prescriber about any you notice.
Should I increase my asthma medication during hay fever season?
Follow your written asthma action plan, which should say what to do if your symptoms get worse. Through the season, keep taking your preventer every day, use a steroid nasal spray every day starting about two weeks before your season, and carry your reliever. Do not change your preventer dose without advice, but contact your GP or asthma nurse if you are needing your reliever more often or your asthma is getting worse.
What antihistamines are safe to take with asthma?
Non-drowsy antihistamines such as cetirizine, loratadine and fexofenadine are safe to take with asthma inhalers and are suitable for treating hay fever. Older, drowsy antihistamines such as chlorphenamine are generally not the first choice for regular use because of drowsiness. For hay fever that is more than mild, a steroid nasal spray such as beclometasone, fluticasone or mometasone, used every day, works better than an antihistamine and is the first choice in people with asthma.
Why do some people get asthma attacks during pollen season?
In people with allergic asthma, breathing in pollen can inflame and narrow the airways directly, and untreated hay fever adds to that inflammation through the shared lining of the nose and lungs. Thunderstorms in the pollen season are a particular risk: they can break pollen grains into tiny fragments that reach deep into the lungs and cause sudden, severe attacks, even in people whose asthma is usually mild. Taking your preventer every day and treating your hay fever lowers the risk.
References
- NHS. Hay fever. nhs.uk
- National Institute for Health and Care Excellence. Clinical Knowledge Summary: Allergic rhinitis. cks.nice.org.uk
- British Society for Allergy & Clinical Immunology. BSACI guideline for the diagnosis and management of allergic and non-allergic rhinitis. bsaci.org
- Joint Formulary Committee. British National Formulary: antihistamines, allergen immunotherapy and allergic emergencies. bnf.nice.org.uk
- electronic Medicines Compendium. Summaries of Product Characteristics. medicines.org.uk
- Met Office. Pollen forecast and the UK pollen calendar. metoffice.gov.uk
- National Institute for Health and Care Excellence, British Thoracic Society and SIGN. Asthma: diagnosis, monitoring and chronic asthma management (NG245), 2024. nice.org.uk
- MHRA. Montelukast: reminder of the risk of neuropsychiatric reactions. Drug Safety Update. gov.uk
Medical disclaimer: This article is for informational purposes only and does not constitute medical advice. Allergy medicines differ in how much drowsiness they cause and in who can take them, and decongestant nasal sprays are not for long-term use. If you have asthma, breathing symptoms that worsen alongside hay fever need review rather than more antihistamine. Always consult a qualified healthcare professional for diagnosis and treatment. In a medical emergency, call 999.