A food allergy occurs when the immune system overreacts to a normally harmless substance in a food by producing antibodies. This type of reaction often runs in families and can strike at any age. It may also cause a wide range of symptoms from a runny nose and headache to a potentially life threatening reaction suffered by those who are allergic to nuts, for example.

An allergy is everything from a runny nose, itchy eyes and palate to skin rash. It aggravates the sense of smell, sight, tastes and touching causing irritation, extreme disability and sometimes, fatality.

Allergic reactions are caused by substances in the environment known as allergens. Allergens contain protein, which is often regarded as a constituent of the food we eat. There are some non-protein allergens which include drugs such as penicillin.

An allergic person's immune system believes allergens to be damaging and so produces a special type of antibody (Ige) to attack the invading material. This leads other blood cells to release further chemicals (including histamine) which together cause the symptoms of an allergic reaction.

A intolerance is often caused by a digestive problem.