Allergic Conjunctivitis
Allergic conjunctivitis is inflammation of the conjunctiva caused by an allergic reaction.
The conjunctiva contains a large number of cells from the immune system (mast cells) that release chemical substances (mediators) in response to a variety of stimuli (such as pollens or dust mites). These mediators produce inflammation in the eyes, which may be brief or long-lasting. About 20% of people have some degree of allergic conjunctivitis.
Seasonal allergic conjunctivitis and perennial allergic conjunctivitis are the most common types of allergic reaction in the eyes. Seasonal allergic conjunctivitis is often caused by trees or grass pollens, leading to its typical appearance in the spring and early summer. Weed pollens are responsible for symptoms of allergic conjunctivitis in the summer and early fall. Perennial allergic conjunctivitis occurs year-round; it is most often caused by dust mites, animal dander, and feathers.
Vernal conjunctivitis is a more serious form of allergic conjunctivitis in which the stimulant is not known. The condition is most common in boys, particularly those younger than 10 who also have eczema, asthma, or seasonal allergies. Vernal conjunctivitis typically reappears each spring and subsides in the fall and winter. Many children outgrow the condition by early adulthood.
Symptoms
People with all forms of allergic conjunctivitis develop intense itching and burning in both eyes. Although usually equal, occasionally, one eye may be more affected than the other. The conjunctiva becomes red, and sometimes the conjunctiva swells, giving the surface of the eyeball a puffy appearance that many people find disturbing. With seasonal and perennial conjunctivitis, there is a large amount of thin, watery discharge. Vision is seldom affected.
With vernal conjunctivitis, the eye discharge is thick and mucuslike. Unlike other types of allergic conjunctivitis, vernal conjunctivitis often affects the cornea, and painful ulcers develop. These ulcers cause extreme sensitivity to bright light and sometimes lead to a permanent decrease in vision.
Diagnosis and Treatment
Doctors recognize allergic conjunctivitis by its typical appearance and symptoms. The condition is treated with allergy eye drops. Such drugs include cromolyn, lodoxamide, olopatadine, and antihistamine eye drops, such as emedastine and levocabastine. Ketorolac eye drops have anti-inflammatory properties and help relieve symptoms. Corticosteroid eye drops have more potent anti-inflammatory effects; however, they should not be used for more than a few weeks without close monitoring because they may produce increased pressure in the eyes (glaucoma), cataracts, and an increased risk of eye infections. Recently, eye drops that block both the release and the effects of the inflammatory mediators, such as azelastine, nedocromil, and pemirolast, have been used successfully.
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