When one person's food can be another's poison

By ROHAN AMERATUNGA

Some people with food allergies may get help in the future from new treatments.

If promising studies in the United States are successful, they may fundamentally change the way we treat people with allergies and finally offer a cure.

Allergies to foods and other environmental substances such as pollens, are mostly caused by antibodies of the IgE class. People who have an allergy or allergies may make IgE antibodies against proteins in foods.

When they consume these foods, the IgE antibodies trigger the release of chemicals from cells known as mast cells and basophils, causing an allergic reaction.

This can range from mild abdominal discomfort to - in a severe allergic reaction - death. In the US studies the receptors for IgE antibodies on mast cells and basophils are being blocked.

In recent years it has become apparent that the spectrum of food allergies is considerably broader than previously suspected. Studies from Johns Hopkins Hospital in the United States have shown that up to one third of children with eczema have a food allergy as a major trigger for their rash.

Along with other treatments, a strict elimination diet can help to control eczema. An allergy to some foods can improve over time. An allergy to milk and eggs will end, in most cases, by late childhood. In contrast, nut and seafood allergies tend to be life-long.

There is no specific treatment for food allergies at present, apart from strict avoidance. It is very important that the offending food is correctly identified, including by skin tests and sometimes blood tests, so that it can be avoided.

Consultation with a dietitian can ensure that the person is on a nutritionally sound diet.

Individuals with life-threatening allergies should carry adrenalin and obtain a medical alert bracelet.

We are fortunate that several voluntary organisations such as the Allergy Awareness Association are able to assist patients and families with allergies.

Not all adverse food reactions are caused by allergies, however. For example, some people lack the enzyme lactase which is needed to digest lactose, so they are unable to tolerate milk products

* Dr Rohan Ameratunga is an Auckland clinical immunologist.