The eye's reaction to allergy-causing substances like pollen and dander, which usually includes redness, tearing, and itching of the eyes.

When your eyes are exposed to a substance to which you are allergic, histamine is released and the blood vessels in the conjunctiva become swollen. (The conjunctiva is the clear membrane that covers the "white" of the eye.) Reddening of the eyes develops quickly and is accompanied by itching and tearing.

Allergies tend to run in families, although no obvious mode of inheritance is recognized. The incidence of allergy is difficult to determine, because many different conditions often are lumped under the term allergy. Keep in mind that rubbing the eyes makes the situation worse.

• May be seasonal
• Red eyes
• Dilated vessels in the conjunctiva (the clear membrane that covers the "white" of the eye)
• Intense itching or burning eyes
• Tearing (watery eyes)
• Puffy eyelids, especially in the morning
• Stringy eye discharge

• The presence of eosinophils (a type of white blood cell) in scrapings, secretions, or discharge
• A positive skin test for suspected allergens (see allergy testing)
• A pattern of small, raised bumps on the inside of the eyelids (papillary conjunctivitis)

The best treatment is avoiding exposure to the cause or allergen; unfortunately, this is not often practical. Discomfort can be relieved by applying cool compresses to the eyes or taking oral antihistamine preparations (many of these are available over-the-counter).

For episodes unrelieved by the above, treatment by the health care provider may be necessary. This may include:

• Administering topical ophthalmic antihistamine or anti-inflammatory drops
• Administering mild topical ophthalmic steroid preparations for severe reactions

Treatment usually relieves the symptoms. However, the condition tends to recur if exposure to the offending agent continues.

There are no serious complications; persistent discomfort is common.

Call for an appointment with your health care provider if you experience allergic conjunctivitis and it is unresponsive to home treatment.

Prevention of allergic conjunctivitis is best accomplished by avoiding the allergen, if it is known. In many cases, however, this is impossible since the allergy-causing agents are everywhere nearly all the time.