An allergy is an abnormal reaction of the body to a substance that is normally harmless to most people. The substance that causes the allergy is called an allergen. Airborne allergens such as pollens and mold spores come in contact with the body through the nose, mouth and eyes, so it is not surprising that an allergic reaction to airborne substances affects these areas of the body directly. Part of the immune response is the release of histamine and other chemicals by the body's tissues. It is the release of these chemicals that cause the itching, tissue swelling and mucus production that comes with airborne allergies.
Allergies are common among children and adults.
Heredity, environment, the number and type of exposures to particular allergens, stress, and other variables can all affect a person's disposition to allergy. Allergies, in turn, can trigger or worsen certain medical conditions such as eczema and asthma, so careful attention must be paid to these conditions. Although there is no known way to prevent allergies there are treatments that will alleviate symptoms. Avoiding an allergen altogether is the best treatment, but obviously that can be impossible with airborne allergens. Luckily, there are effective drugs and other treatments.