A vasoconstrictor is the most commonly used medication. This type of drug shrinks the congested blood vessels in the conjunctive and reduces swelling. These drugs are available as eye drops, and many do not require a doctor's prescription. Other medications may be needed for comparatively severe and acute allergic conjunctivitis. Some eye drops combine a vasoconstrictor and an antihistamine.
Antihistamines relieve itching and tearing by blocking the action of histamine.
When the allergic reaction involves parts other than the eyes, oral antihistamines may be helpful. Another type of eye drop actually inhibits the release of histamine from one of its main sources in the body, the mast cells. Patients with severe allergic conjunctivitis may need to use any or all of the above medications with the addition of corticosteroid drops. Steroids should not be used over a long term as prolonged use may lead to cataracts or glaucoma in some patients. The goal of therapy is to reduce symptoms to a tolerable level using as little medication as possible.