The body of a person with an allergy responds to an allergen by attacking it. The immune response activates certain immune cells called mast cells. Mast cells trigger the release of chemicals. These chemicals include histamine and leukotrienes. They act on tissues in the body and create the allergic response.
Allergies can affect nearly any part of the body.
The nose, sinuses, eyes, lungs, and skin are most affected. No one knows for sure why some people have allergies and others do not. Family history appears to play a part in a person's development of allergies. There is little that can be done to prevent allergies from developing. Once they have developed, flare-ups can be reduced by allergy shots.