What Causes Allergies?
Allergies tend to run in families. If you have allergies, it's very likely that at least one of your parents does too.
Exposure to allergens at times when the body's defenses are weak, such as after an illness or during pregnancy, also may play a role in developing allergies. Although allergies are most common in children, they can occur at any time and any age. Sometimes allergies go away, but they also can come back years later.