An allergy is the body's reaction to a substance - known as an allergen - which does not normally produce adverse effects in the majority of people. Allergens can be encountered in different environments and in different ways such as by breathing, eating or drinking, touching, being near or having them injected into your body.
The body's immune system produces different antibodies to fight viruses and bacteria in the body and when you have an allergy, the immune system overreacts and produces antibodies that react against allergens. These antibodies react on the surface of cells in the body, which are found on the lining of the nose, skin, lungs and intestines. When allergens come into contact with these cells, they release chemicals, including histamine, which produce changes in the body, such as hives, swelling of the nose and chest, mucus production and other "inflammatory" symptoms.
Typical causes of allergies include:
Non-food Allergens
- Pollens (trees, grasses, weeds)
- Moulds
- Dust mites
- Animal products (skin, saliva, urine)
- Drugs
- Latex
- Insects
Food Allergens
- Peanuts
- Nuts
- Shellfish
- Fish
- Milk
- Eggs
- Wheat
- Soy and Soya
- Sesame seeds