Allergy (or atopy) is an abnormal or exaggerated reaction by the body to certain foreign proteins. In these allergic people the body produces an inflammatory response to these proteins which are called allergens. This abnormal inflammatory response is present in all common allergic conditions. Allergens do not produce an inflammatory response in people who are not allergic.
Common allergens are:
- House dust mite
- Foods, e.g. cows milk protein, eggs, wheat, peanuts, fish and soya
- Pollens, e.g. grass or tree pollen
- Dog and cat hair
- Fungus (mould) spores
In allergic people the body responds abnormally to foreign proteins by producing IgE rather than IgG (atopy).