By Dr Milton Lum

THERE are instances in which an allergic reaction is severe and sudden that it poses a threat to the life of the affected individual, if immediate medical treatment is not provided. This condition, which is called anaphylaxis, is, fortunately, uncommon.

Causes

An individual's immune system becomes sensitised to an allergen after an initial exposure.

Upon a subsequent exposure, a severe reaction involving the whole body may occur. The different parts of the body release mediators like histamine and other substances, which cause the airways to tighten and leads to other features.

Anaphylaxis is unpredictable as it can occur at any time. Some people get it and others do not. It usually occurs in patients who have an allergy.

There are several substances that can cause anaphylaxis if the body is exposed to it. The common causes are foods like peanuts, tree nuts, eggs, cow's milk and seafood; insect bites like bee stings; and medicines like antibiotics.

Pollen and other inhaled substances are rare causes of anaphylaxis.

Anaphylaxis can occur after exposure to a small amount of the allergen.

There are occasions when anaphylaxis occurs only when there are certain conditions present. For example, exercise induced anaphylaxis (EIA) occurs only when the individual exercises after exposure to certain food or medicines. The food or medicines, by itself, does not produce symptoms.

The EIA occurs only after the individual exercises after taking the food or medicines.

There are some individuals who develop anaphylaxis for no apparent reason. Attempts at identifying the trigger for the severe allergic reaction can draw a blank. This condition is called idiopathic anaphylaxis.