Allergic conjunctivitis is inflammation of the conjunctiva caused by an allergic reaction.
Allergic reactions caused by, for example, airborne allergens, may inflame the conjunctiva.
Redness, itching, swelling, tearing, and stringy discharge are common.
Various eye drops may help decrease symptoms and inflammation.
The conjunctiva (the membrane that lines the eyelid and covers the white of the eye) contains a large number of cells from the immune system (called mast cells) that release chemical substances (called mediators) in response to a variety of stimuli (such as pollens, mold spores, or dust mites). These mediators cause inflammation in the eyes, which may be brief or long-lasting. About 20% of people have some degree of allergic conjunctivitis. (See also Overview of Conjunctival and Scleral Disorders.)
An Inside Look at the Eye
Seasonal allergic conjunctivitis (hay fever conjunctivitis) and year-round or perennial allergic conjunctivitis (atopic conjunctivitis, atopic keratoconjunctivitis) are the most common types of allergic reaction in the eyes. Seasonal allergic conjunctivitis is often caused by mold spores or tree, weed, 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 and is most often caused by dust mites or animal dander.
Vernal keratoconjunctivitis is a more serious form of allergic conjunctivitis in which the stimulant (allergen) is not known. The condition is most common among boys, particularly those aged 5 to 20 years who also have eczema, asthma, or seasonal allergies. Vernal keratoconjunctivitis typically reappears each spring and subsides in the fall and winter. Many children outgrow the condition by early adulthood.
Inflammation of the conjunctiva caused by a virus or bacteria, as opposed to an allergic reaction, is called infectious conjunctivitis.
Symptoms of Allergic Conjunctivitis
People with all forms of allergic conjunctivitis develop intense itching and burning in both eyes. Although symptoms usually affect both eyes equally, rarely one eye may be more affected than the other. The conjunctiva becomes red and sometimes swells, giving the surface of the eyeball a puffy appearance. The eyelids may become intensely itchy. Rubbing and scratching leads to eyelid skin redness, swelling, and a crinkly appearance.
DR P. MARAZZI/SCIENCE PHOTO LIBRARY
With seasonal allergic conjunctivitis and perennial allergic conjunctivitis, there is often a large amount of thin, watery discharge. At times the discharge is stringy. Vision is seldom affected. Many people have an itchy, runny nose.
With vernal keratoconjunctivitis, the eye discharge is thick, stringy, and mucuslike. Unlike other types of allergic conjunctivitis, vernal keratoconjunctivitis often affects the cornea (the clear layer in front of the iris and pupil), and in some people painful, small, open sores (corneal ulcers) develop. These ulcers cause deep eye pain with exposure to bright light (photophobia) and sometimes lead to a permanent decrease in vision.
Diagnosis of Allergic Conjunctivitis
A doctor's evaluation of the symptoms and appearance of the eye
Doctors recognize allergic conjunctivitis by its typical appearance and symptoms. Tests are rarely needed or useful.
