Conjunctivitis is an inflammation of the conjunctiva. The condition is very common since the conjunctiva is exposed to many substances that can cause infection or an allergic reaction. Conjunctivitis can be either acute or chronic. An acute condition is one that flares up suddenly and lasts a fairly short time. A chronic condition is one that lasts for a long time, usually many years.

Conjunctivitis can affect one or both eyes. If caused by an infection, it can usually be transmitted to other people quite easily. The disease is very common among children in day care or schools. In such settings, children come into close contact with each other and conjunctivitis spreads quickly throughout the group. The disease is also known by the name of pink eye or red eye. These names come from the physical appearance of the eye as a result of conjunctivitis.

Conjunctivitis can be caused by a bacterial or viral infection; by certain environmental factors, such as smoke, dust, or pollen; or by other factors. Viruses cause many kinds of infections, such as the common cold (see common cold entry), acute respiratory infections, or diseases such as measles (see measles entry). These infections can spread easily to the eye. If they infect the conjunctiva, conjunctivitis results.

Symptoms of conjunctivitis can range from mild to serious. They can affect one eye or both. Some common symptoms include redness of the eye, swelling of the eyelid, and a discharge from the eye. The discharge is watery and either yellow or green in color. Some kinds of viruses cause more serious reactions. They may cause the eye to feel scratchy and have a pus-like discharge. These infections also can cause swelling and tenderness of the lymph nodes behind the ear.

Bacterial infections of the conjunctiva also cause redness of the eye and swelling of the eyelids. They may produce a pus-like discharge that turns crusty during the night. Some forms of bacteria that cause sexually transmitted diseases (see sexually transmitted diseases entry), such as gonorrhea, can also cause conjunctivitis. Infections of this kind may result in intolerance to light and tenderness in the lymph nodes behind the ear. These symptoms may last up to three months.

Some environmental conditions that cause conjunctivitis include wind, smoke, dust, pollen, and grass. As with infections, these factors can cause redness in the eye, swelling of the eyelid, and discharge from one or both eyes. Chemicals in contact lens solutions can sometimes produce similar reactions. Less common causes of conjunctivitis include exposure to sun lamps and problems with the tear ducts, the structures that produce tears for the eyes.

Diagnosis of conjunctivitis is usually based on a medical history and physical examination. A doctor will ask when the symptoms began, how long the condition has been going on, the symptoms experienced, and if the patient has had any recent infections or diseases. Contact with anyone who has had conjunctivitis is also important information.

Diagnosis is usually relatively simple because symptoms are obvious. In rare cases, smears may be taken. A smear is obtained by collecting discharge from the eye on a cotton swab. The discharge can then be kept in a warm place until any bacteria that are present begin to grow. The bacteria can then be studied under a microscope.

The treatment of conjunctivitis depends on the cause of the condition. In all cases, symptoms are usually relieved by the use of a warm compress placed directly on the eye. A compress is a moist pad. The treatment is repeated several times a day.

There are relatively few direct treatments for viral infections. If a herpes infection is suspected, medical advice should be sought. A herpes infection is one caused by a herpes virus (see herpes infections entry). The herpes virus causes a variety of infections, including cold sores and infections of the genital area. Sometimes antibiotics are used to prevent secondary infections. A warm compress is advised to relieve discomfort. The viral infection usually clears up after a few days.

Bacterial conjunctivitis can be treated with antibiotics. Ointments (lotions) or eye drops containing the antibiotic can be placed directly into the eye. The treatment is usually used once a day for one or two weeks. Improvement is usually seen in the first three days. If there is no change, a different drug may be needed, or another cause for the infection should be considered.

Cases of conjunctivitis related to sexually transmitted diseases require special types of care. In some cases, injections of antibiotics may be necessary. Sexual partners should also be notified and treated.

Cases of conjunctivitis caused by environmental factors are treated by removing the agent responsible for the problem. For example, a person who is allergic to dust or pollen should try not to be exposed to these substances. Symptoms can be treated with a cool compress applied directly to the eye. Drugs such as diphenhydramine hydrochloride (pronounced DIE-fen-HI-druh-meen HI-dro-KLOR-ide, trade name Benadryl) can also provide relief when administered as eye drops.