What is allergic conjunctivitis?

Allergic conjunctivitis is an allergic reaction on the surface of the eyes. It is a very common condition that occurs when your eyes come in contact with allergy-causing substances (allergens). Pollen, cat dander, and smoke are examples of such substances.

How does it occur?

The allergens may be in the air, such as smoke or plant pollen. Or they might be on your hands and get into your eyes when you touch your eyes.

Repeated encounters of the eyes with an allergen cause the body to produce antibodies on the surface of the eyes. When the allergen floating in the atmosphere contacts the antibody on the eye, an allergic reaction begins. The eye releases chemicals, including one called histamine, that cause the symptoms of allergic conjunctivitis.

What are the symptoms?

The symptoms are itchy, watery eyes that are often red and sometimes swollen. Both eyes are affected unless just one eye came into contact with the allergen, as might happen with poison ivy.

How is it diagnosed?

The diagnosis of allergic conjunctivitis is usually made from your medical history. Sometimes your family history is also helpful. Tests for reactions to specific allergens may be done if you have a severe case of conjunctivitis that does not respond to the usual treatment.

How is it treated?

The first choice for treatment is to avoid the allergy-causing substance(s).

The second choice is medication. Some people need to take antihistamine tablets by mouth, especially if they have other allergy symptoms. If you have only eye symptoms, eye drops may be the only medication you need. Two relatively new types of eye allergy drops appear to be quite effective: one is an anti-inflammatory medication and the other is an antihistamine. Both types of drops require a prescription from your doctor. Some people can use eye drops on an as-needed basis; for example, just before mowing the lawn. Others need to use the drops daily during their allergy season to prevent more severe symptoms.

How long will the effects last?

The symptoms of allergic conjunctivitis will last as long as the allergen is present, whether it's spring pollen or cat dander in a carpet. If allergic reactions began when you were a child and have persisted to early adulthood, they will likely occur throughout your life. Anybody, however, may develop an allergy, including allergic conjunctivitis, at any time in his or her life.

Occasionally a person will develop an eye infection (bacterial conjunctivitis) in addition to the allergic conjunctivitis. Bacteria may get into the eyes when they are scratched or rubbed.

What can be done to help prevent allergic conjunctivitis?

Often there is no way to prevent allergic conjunctivitis. You can try to lessen your symptoms by limiting your exposure to allergens. For example, avoid going outside when pollen counts are highest or when the wind is blowing allergens through the air. Use air conditioning rather than opening windows. Avoid using attic fans.

Severe symptoms may require allergy testing and a series of allergy shots for 12 to 24 months.