Jeremy Laurance: When nature's weapon of mass destruction strikes

For millions of Britons, the symptoms will be familiar: red, hot itchy eyes, a sore throat and a runny nose.

Hay fever, or allergic rhinitis, is a reaction to substances present in the air and this summer it looks set to bring record cases in the UK.

The problem lies in pollen, which could be described as nature's weapon of mass destruction. In people sensitive to it, it lays waste to the nose, eyes, throat, lungs, skin and mouth. The tiny grains provoke an allergic reaction that makes tissues swollen, red, hot, itchy and irritable.

Those afflicted began suffering in April with the arrival of tree pollen, of which birch is the worst.

The grasses that cause most hay fever, affecting 95 per cent, start to flower this month, releasing their pollen into the atmosphere. The season peaks next month.

Anti-histamines and steroid nasal sprays are the standard medical treatments and many can be bought over the counter, but are expensive. Generic versions of branded medicines can be significantly cheaper. One, Clarityn, an anti-histamine, costs £4.45 for a pack of seven tablets. Superdrug sells a generic version containing the same amount of the active ingredient, loratadine, for half the price. Some dislike anti-histamines because they make them drowsy, but newer versions on the market are claimed to be non-sedating.

For the worst-affected sufferers, vaccination is an option. It involves weekly injections for eight weeks, followed by monthly injections for three years and, rarely, it produces a severe adverse reaction.

The medical establishment is divided as to what further aggravates hay fever sufferers, although one factor is pollution, especially traffic pollution. Chemicals from vehicle exhausts are thought to be sensitising the airways of susceptible individuals, making them more prone to allergies.

At the same time, proteins on the pollen grains may be washed off and attach themselves to particles in the polluted air which, because they are so much smaller, can be drawn more deeply into the lungs, increasing the risk of an allergic reaction.

Another factor may be our sterile modern environment.

The growth of antibiotic use in childhood and the growing schedule of vaccinations that keep viruses at bay may also play a role. But at the same time, children are spending more time indoors than in the past where in their centrally heated, double-glazed homes they are exposed to higher levels of certain allergens including house dust mites and cat hair - a form of indoor pollution. This in turn sensitises them to pollen.

What is clear is that record numbers are suffering. One study, presented to the European Society of Allergy and Immunology, showed that 26 per cent of the UK population were hay fever sufferers, twice the level of two decades ago.

How to resist hay fever

* Keep windows shut

* Avoid going out in the evening, when pollen counts are highest (the pollen grains rise in the day and fall back to earth in the evening)

* Avoid open grassy spaces

* Take a holiday near the coast, where pollen counts are lowest

* Dry washing indoors to avoid pollen clinging to fabrics and being brought into homes

* Wear sunglasses - they help to prevent (and disguise) itchy eyes

* Consult one of the dozen NHS full-time allergy clinics. Contact them via Allergy UK on 01322 619864 or www.allergyuk.org