Allergic Conjunctivitis

Allergic conjunctivitis is inflammation of the conjunctiva (the clear membrane covering the 'white' part of the eyes) due to a reaction from allergy-causing substances such as pollen and pet dander.

If allergic conjunctivitis is combined with rhinitis, the condition is termed allergic rhinoconjunctivitis.

Causes and Development

When the eyes are exposed to allergens such as pollen, animal dander / saliva, or molds, histamine is released and the blood vessels in the conjunctiva become swollen, resulting in rapid reddening of the eyes, itching and tearing.

Other causes include perfumes, cosmetics, skin medicines, air pollution and smoke, dust mites or eye drops.

Signs and Symptoms

Symptoms are due to release of histamine and other active substances by mast cells and may include red eyes, dilated vessels in the clear tissue covering the whites of the eyes, itching and/or burning eyes, swollen eyelids, watery eyes, or stringy eye discharge.  Itching is the most common symptom, reported by 75% of patients.

Symptoms are usually made worse by warm, dry weather, and improved by cool, rainy weather.

Treatment and Prevention

Recommendations include cold compresses, anti-inflammatory eye drops, or mild eye steroid preparations applied directly to the eyes for severe reactions.

When cold compresses are no longer effective, mast cell stabilizers (eye drops that prevent mast cells from releasing histamine) may be used in combination with antihistamines.  It takes a longer time for them to work, but they have fewer side-effects and work much longer than antihistamines.