An allergy is an exaggerated reaction by the immune system in response to exposure to certain foreign substances. These foreign substances are normally seen as harmless by the immune system in nonallergic individuals, but in allergic individuals, part of the immune system generates a response.
When an allergic individual comes in contact with an allergen, the immune system mounts a response through an antibody called immunoglobulin E (IgE). People prone to allergies are said to be allergic or "atopic."
Allergy-producing substances are called "allergens." For instance the allergens comprise of :
- Pollens
- Dust mites
- Molds
- Animal proteins
- Foods
- Medications