Seasonal wheezes and sneezes...

Dr Harry Morrow-Brown looks at the seasonal nature of inhaled allergies - and how to defeat them

To live we must breathe, but along with the summer air we must also inhale pollens and mould spores. These microscopic particles stick to the moist lining of the nose, the eye, and the bronchial tubes. They do not harm normal people, but in allergic subjects they can cause hay fever and/or asthma.

The main culprits are tree pollens in spring, grass pollen in June and July, and mould spores from July to October. The moment a pollen grain or mould spore sticks to the moist lining of the nose, the eye, or the bronchi the allergen begins to dissolve. If that person is allergic to pollen or spores an immediate reaction occurs causing sneezing in an attempt to reject the allergen.

The allergen is released very quickly into the sensitised cells of the respiratory tract triggering the release of irritating chemicals such as histamine. Repeated inhalation of thousands of pollen grains or mould spores day after day causes incessant sneezing, nasal congestion and blockage, itchy inflamed eyes, and sometimes asthma.


In dry windy weather lots of pollen is blown off the grass so that the pollen count, (the number of pollen grains in a cubic metre of air), can vary from hour to hour, usually being at a maximum on sunny breezy evenings. Heavy rain washes the pollen out of the air so most sufferers feel much better after rainfall. However, very heavy rain, as in a thunderstorm, can break up the pollen grains and liberate huge numbers of tiny, highly allergenic granules. These are so small that they can penetrate deep into the lungs and cause ‘thunderstorm asthma’, when large numbers of severe asthma cases arrive in hospitals at about the same time.

Moulds & Yeasts

In the damp British climate the summer pollen season is followed by the mould spore and yeast season, which lasts until late October. This also causes hay fever and, more often, late seasonal asthma.
Millions of mould spores get airborne during the day, and because spores are much smaller than pollen grains they are more easily inhaled into the depths of the lung. In the early hours of the morning billions of yeasts appear in the air, and many asthmatics will have a severe attack.

In damp weather enormous numbers of yeasts will persist in the air through the day, so patients do better to keep windows shut at night.
In the unusually dry summer of 1976 many patients found that their hay fever and asthma was much better, because the main cause of their summer problems was moulds and yeasts rather than grass pollen. Many patients who are sensitive to mould spores do not get better until the first frost, when the cold stops the mould spores being shed into the air. Recent mild winters have given little relief to mould sensitiv patients unless they take a holiday in a nice warm, dry climate.

When desensitisation injections were permitted it became evident that in damp years patients who had been effectively desensitised to grass pollen were worse in wet weather than in dry! The reason was that before treatment to abolish their pollen sensitivity they were miserable in both wet and dry weather, and afterwards they were still sensitive to the moulds and yeasts.

Most sufferers try to avoid pollen by staying inside as much as possible, especially in the evening, keeping car windows shut, having a pollen filter in their car, and taking antihistamines or nasal steroid sprays. In milder cases this is often effective, but attacks can still be triggered by unexpected violent fluctuations in the pollen count.


Twenty years ago injections of gradually increasing doses of pollen extracts to desensitise sufferers from hay fever and asthma were stopped in this country because of severe reactions. Since then, Britain, alone in the world, has relied entirely on suppressive drugs for treatment.

However, this year two methods of desensitising grass-pollen allergic patients who cannot obtain relief from drugs, experience trying side effects, or for whom oral steroids are contraindicated, have become available on the NHS.

Patients have to be referred by their GP to a specialist clinic to obtain this treatment, but it is possible to get treatment privately. Treatment has to be started at least two months before the season.

The first method of treatment, ‘Grazax’, does not involve injections. It is self-administered by dissolving small pills under the tongue every day, and is called ‘sub-lingual immunotherapy’ or SLIT for short. Full information is easily found on the internet at and it has already been approved in most European countries.
I carried out the first trial of SLIT in the UK as long ago as 1976, and also a double blind trial from 1984 to 1989 using liquid extracts of grass pollen. The excellent results I obtained are to be found on my website However, general availability has had to await the development of the special pills containing pollen extract, and further clinical trials showing safety and efficacy.
In the last 20 years SLIT has been tried out extensively in Europe, using different pollens and dust mites. It has been shown to be safe and, because injections are unnecessary, it is becoming
increasingly popular, especially for children. It may well be the most practical future method of specific immunisation for allergies.

The second method of treatment called ‘Pollinex’ consists of four, weekly injections of either grass pollens or tree pollens. This has also been authorised for NHS treatment of patients who do not benefit from drug treatment. Very large clinical trials in Europe have shown that, by using specially modified extracts of pollens and other allergens, the immune response to injections can be boosted effectively by just four, weekly injections. Again safety has been established, and private prescribing is possible. Further details from

Hay Fever

Many hay fever victims have a poor quality of life in summer, while their daily efficiency is impaired both by the allergic reaction and by the drugs used to control it. Most use antihistamines, steroid nasal sprays or herbal remedies and just ‘put up with it’ assuming,
incorrectly, that their GP will be unable to help.

Steroid nasal sprays are effective especially if treatment is commenced a week before the sufferer knows, from previous experience, the hay fever is due to begin. The spray should be used every day whether there are symptoms or not, supplemented with antihistamine tablets if necessary, until the season is over. Inhaled steroids are not effective in severe cases because of blockage and congestion.

This regime makes sense as, if the nose gets blocked, nasal sprays become useless. The antihistamine from the chemist may be less effective than those available on prescription, and older antihistamines, such as chlorpheniramine (Piriton) may cause dangerous drowsiness, especially when driving.


Long lasting steroid injections were given for hay fever for many years. They were effective but the dose was large, and the drug released over six weeks at a constant rate, which bore no relationship to the pollen count. Moreover, if the injection was given too soon, it could ‘run out’ before the end of the season necessitating another injection. More importantly, this treatment has been occasionally associated with necrosis of the head of the femur, leading to hip replacement.

Oral steroids

In really severe cases of hay fever, oral steroid tablets can be taken for a few days only when the hay fever is at its worst. An important occasion fully justifies prescribing this very effective treatment. Because they are taken for a short time only, there is no significant risk of side-effects. Three steroid tablets a day, usually prednisolone 5mg, taken when the symptoms become intolerable, or just before the special event, will usually abolish the hay fever and all other symptoms.

Pollen asthma

In a minority of patients the bronchi also become sensitised to pollen because tiny granules from the pollen grain reach into the smallest bronchi to cause asthma,which can be very severe. Pollen counts are unpredictable and fluctuate wildly. I have observed an average hourly pollen count of 150 for the day while the peak count was over 1000.
Any asthmatic who is aware that they have severe asthma every summer should consult their doctor in late May or early June so that effective treatment can be commenced to prevent the development of dangerous attacks, which can happen with little warning.

Severe night-time asthma can be caused by a delayed reaction to pollen inhaled during the day. For example, a man who was very pollen sensitive drove from London to Derby in a car without a pollen filter. He checked into his hotel, did not come down for dinner and was found dead in the morning.

In the spring, tree pollens get into the air in large numbers,
especially near or under birch trees where the pollen counts can be very high. These pollens cause the same problems as grass pollens, but the season is shorter.

For further information on all manner of allergies and intolerances check out Dr Morrow Brown’s website at - email for advice or a consultation.


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First Published in 2007

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