An allergy is an exaggerated response to substances that, in most individuals, cause no difficulty. Allergy is a name given to the way your body reacts when it mistakes ordinarily harmless substances (like grass, tree or weed pollen) for something harmful.
An allergy sufferer's immune system overreacts to pollen. Seasonal allergic rhinitis, also called hay fever, occurs in the spring and fall when the air is full of pollen-- particularly here in the agriculturally-rich San Joaquin Valley.
A substance that causes the exaggerated response is called an allergen. Allergies are among the most common diseases experienced by Americans. They are believed to complicate the lives of as many as 40 million adults and children in the United States. That means allergies are the country's sixth most prevalent chronic condition.