Food Allergy

An allergy is caused when the body mistakenly makes an antibody (IgE) to 'fight off' a specific food or substance. When the same substance is next eaten (or is injected, or sometimes is just in contact with the skin, or is inhaled) it triggers an immune system response which results in the release of histamine and other naturally occurring chemicals somewhere in the body. These chemicals cause various symptoms, depending on where in the body they are released. For example, in the gut they may cause abdominal pain, vomiting and diarrhoea; in the skin, itching and swelling (rash or nettlerash); in the upper airways, a runny nose or sneezing; in the lower airways, a wheeze or cough.

Histamine causes symptoms to develop quickly, but the reaction doesn't usually last very long. However the other chemicals that are released as part of the immune response have a more delayed effect and can produce symptoms starting after a few hours, and lasting into the following day or beyond. This may lead to 'chronic' symptoms such as eczema.

Very rarely the immune system chemicals are released throughout the whole body instead of just in one or two areas, causing a 'systemic' reaction (anaphylaxis). As well as symptoms such as itching, abdominal pain and vomiting, there can be more serious problems such as severe wheezing, swelling of tissues of the face, throat and airways, and a sudden drop in blood pressure. It is important to realize that these symptoms are not always life-threatening, but also to understand that they can be, if not treated promptly. Anyone suffering a severe allergic reaction should be given any prescribed treatment without delay, and should then be transported to hospital by emergency ambulance.

Most severe reactions are due to an allergic response and can be identified by the blood or skin tests used in NHS clinic allergy testing. Very occasionally the only way to establish a diagnosis is by elimination of offending foods and, if there is improvement, to conduct a double blind challenge in a suitable environment. This should only be carried out in a medical environment with suitable emergency facilities.

If a severe allergy has been identified, it is important that the sufferer should avoid even tiny amounts of their trigger food or substance. Very occasionally, reactions can occur even when the person has had skin contact with the offending food. For example, some peanut allergic people have suffered a severe reaction just through being kissed by someone who has eaten peanuts. A fish-allergic person may react by being in a kitchen where fish is being cooked.

As well as avoiding the offending food, the allergic person should be provided with appropriate emergency treatment should accidental exposure occur. Depending on the severity of reaction, this may be adrenaline to be given by injection, antihistamines, steroids, or all of these. The exact details of such treatment will need to be decided by the doctor in charge of the patient.

Individuals affected by severe food allergy, should still be able to participate in all normal activities, school, work or leisure, but appropriate support and understanding is required.

All people identified as having (or suspected of having) food allergy should be referred to an allergy specialist.

Management

• Wear a 'Medic Alert' or similar bracelet or medallion
• Inform work colleagues, catering staff, occupational health staff, teachers and first-aiders about your allergy.
• Avoid the foods that cause your allergy totally - do NOT risk testing for the presence of your allergen (peanut, egg, milk) in food by eating a small amount - remember that tiny quantities of the allergen can cause a severe reaction.
• Take any medication prescribed for your reaction promptly if symptoms begin. Then call an ambulance or go to hospital immediately (do not travel alone).
• If you have been prescribed an adrenaline auto-injector, carry it with you at all times. Make sure you know how and when to use it, and what other steps to take. Your family and colleagues should also know how and when to give your adrenaline, in case you become unable to give it yourself.

Other Food Reactions

A few people develop immune-system reactions to foods where the IgE 'allergy antibody' is not involved. They may develop 'contact' reactions to foods caused by immune system cell reactions, or by other, more unusual antibodies. The symptoms caused by these reactions are generally more delayed and less severe than IgE allergy reactions, but may lead to chronic symptoms in the gut (pain, diarrhoea, generalized unwellness), especially in children.

Updated 5/2009