Allergic conjunctivitis is an inflammation of the lining of the eyelids. The tissue that lines the eyelids is called the conjunctiva. This inflammation generally is the result of a reaction to common allergens — allergy-causing substances such as dander and pollen. Allergic conjunctivitis can be kept under control with medications that suppress the allergic response.
The cause of allergic reactions is an immune system overreaction to the allergen causing the allergy symptoms. When the eyes come into contact with an allergen, white blood cells in the eye release substances called histamines. These substances cause swelling of blood vessels in the conjunctiva and are responsible for most other symptoms of allergic conjunctiva inflammation.
Symptoms of allergic conjunctivitis often are seasonal. This is particularly the case when an individual is allergic to seasonal allergens such as pollen. Symptoms of this condition include reddening of the eyes, itchy or burning eyes, watery eyes, eye discharge and puffy eyelids. It also is common for the blood vessels at the surface of the eyeball to dilate, causing the appearance of bloodshot eyes.
When testing for allergic conjunctivitis, a doctor might take samples of skin scrapings as well as discharges and secretions from the eye. These samples are tested for white blood cells called eosinophils, which are important facilitators of allergic reactions. The doctor might also examine the eyes to look for characteristic signs of conjunctivitis, such as small raised bumps on the inside surface of the eyelids. Lastly, skin tests for suspected allergens might be performed. These tests involve skin exposure to substances to which the patient is suspected of being allergic.
After allergic conjunctivitis has been diagnosed, the only sure way to prevent symptoms is to avoid contact with the allergenic substance. Entirely preventing exposure is typically impractical, but certain medications and home treatments can be used to help alleviate the symptoms. Over-the-counter oral antihistamine medications usually are sufficient to treat most mild cases of conjunctivitis. Washing the eyes with cool water or applying a cool compress can help soothe the eyes and relieve itching and burning.
These measures are sometimes ineffective for people with severe allergies or when someone has been exposed to a large amount of allergen. In such cases, stronger medication might be needed. Prescription antihistamine medications or eye drops can soothe the eyes more quickly and effectively than over-the-counter oral medications can.
If symptoms are very severe, a steroid preparation might be prescribed for direct application to the eyes. Steroids are effective because they suppress the immune response that causes the conjunctivitis symptoms. These medications cannot be used over the long term, however, because long-term use can suppress the entire immune system and cause other potentially harmful side effects.
