I ONLY WENT to his inaugural lecture out of friendship. Food allergy was not really something I was interested in. Foodies bore me. How wrong I was though. Jonathan Brostoff's lecture was brilliant and his research of major importance.

For over 20 years Brostoff has been running an allergy clinic where patients typically have asthma and chronic hay fever. Indeed, the WHO has recognised that allergy is the number one world environmental disease. The prevalence of some sort of allergy in the population is high, around 15 per cent. In some areas the incidence of childhood asthma is high as 25 per cent. Brostoff became increasingly convinced that in many cases the substance that caused the allergic reaction was food.

He came to his ideas about food and allergy by what he claims was not reductionist science but by listening to what his patients told him. But he had to deal with what he refers to as the "nuts" and the "blimps". The former, patients who were convinced that all their medical problems were due to food, and latter, conservative doctors who claimed that good food never harmed anybody.

The response to foods can be very severe, those who are sensitive to peanuts react with swelling lips almost at once, and the reaction can even lead to death. Intolerance to certain foods has a genetic component - having parents with an allergy increases the likelihood by two- to four- fold. In "identical" twins, if one has an allergy the chance for the other is 50 per cent.

Food taken by infants can effect the likelihood of an allergy developing. Children fed on cow's milk have a two-fold higher incidence of asthma. Incidence is also increased if solids are given before 15 weeks, and in children given antibiotics under the age of two the increase is four-fold.

Many foods can cause an allergic reaction. Eggs can cause a response in less than two hours while with other foods, like wheat, the delay can be as long as six hours, making recognising the connection difficult. To test whether food is the cause of an allergy the patient must be starved. Well, not quite, the patient is put on an astronaut's diet which contains the essential for survival for long periods but no solid food at all. Over one half of parents with allergies improve on the astronaut's diet and by adding back conventional foods one at a time the cause of the allergy can be found.

It is not only those with classical allergic symptoms who do better, but also those with a variety of ailments involving the immune system. This includes those with arthritis, migraine, irritable bowel disease, and even children with behavioural disorders. One child improved markedly on a diet of steak and chips while in France but relapsed when tucking into a bowl of cereal on return.

The mechanism by which foods cause these problems is far from clear. It seems to involve some component altering the wall of the gut and so allowing substances to enter the blood stream, initiating an immune-like response which can attack an organ. Unfortunately, there is no animal model which can be used to investigate the mechanism, diagnosis is difficult - the numerous symptoms increase the complexity - and there is no cast- iron test for food allergy that will satisfy critics. Nevertheless helping a large faction of sufferers of a variety of illnesses is a triumph not only for the relief it gives them, but for the enormous savings it brings to the NHS. His lecture's subtitle was very apt, "An ounce of prevention is worth a pound of cure."