Inflammation of the conjunctiva, the membrane covering the white of the eye and the inside of the eyelids

  • Wearing contact lenses and using cosmetics or eyedrops are risk factors
  • Genetics as a risk factor depends on the type
  • Age and gender are not significant factors

Conjunctivitis, also called pink eye, is a common condition in which the conjunctiva, the clear membrane covering the white of the eye and lining the eyelids, becomes inflamed. The affected eye becomes red and sore and may look alarming, but the condition is rarely serious. One or both of the eyes may be affected, and in some cases it begins in one eye then spreads to the other.


This eye shows signs of conjunctivitis, including swollen eyelids, a discharge, and redness over the white of the eye.

What are the causes?

Conjunctivitis may be caused by a bacterial or viral infection, or result from an allergic reaction or irritation of the conjunctiva, for example by smoke, pollution, or ultraviolet light.

Bacterial conjunctivitis is common, and may be due to several types of bacteria. Viral conjunctivitis can occur in epidemics caused by one of the viruses that causes the common cold. One viral form of conjunctivitis, called herpes keratoconjunctivitis, results from a herpes simplex infection. Conjunctivitis due to viruses or bacteria can be spread by hand-to-eye contact and is highly contagious.

Newborn babies sometimes develop conjunctivitis. This can happen if an infection is transmitted to the baby’s eyes from the mother’s vagina during the birth. This form of conjunctivitis is usually caused by the microorganisms responsible for certain sexually transmitted infections, including chlamydial infection, gonorrhoea, and genital herpes.

Allergic conjunctivitis is a common feature of hay fever and of allergy to dust, pollen, and other airborne substances (see Allergic rhinitis). The condition may also be triggered by chemicals found in eyedrops, cosmetics, or contact lens solutions. Allergic conjunctivitis often runs in families.

What are the symptoms?

The symptoms of conjunctivitis usually develop over a few hours and are often first experienced on waking. The symptoms generally include:

  • Redness of the white of the eye.

  • Gritty and uncomfortable sensation in the eye.

  • Swelling and itching of the eyelids.

  • Discharge that may be yellowish and thick or clear and watery.

The discharge may dry out during sleep and form crusts on the eyelashes and eyelid margins. As a result, the eyelids sometimes stick together on waking.

What can I do?

If you think you may have bacterial conjunctivitis, chloramphenicol drops and ointment are available over the counter to treat the condition in those over 2 years old. To avoid spreading infection, wash your hands after touching the eye and do not share towels or facecloths. Once conjunctivitis has cleared up, sight is rarely affected.

If you are susceptible to allergic conjunctivitis, avoid exposure to triggering substances. Antiallergy eyedrops can be used to ease the symptoms (see Drugs acting on the eye). If conjunctivitis does not clear up with self-help measures or if an eye becomes painful and red, you should consult your doctor.

What might the doctor do?

Your doctor will probably make a diagnosis from your symptoms. If infection is suspected, he or she may take a sample of the discharge to identify the cause.

Bacterial conjunctivitis is treated by applying antibiotic drops or ointment and the symptoms usually clear up within 48 hours. However, the treatment should be continued for as long as recommended by your doctor, even if there is improvement, to ensure the infection is eradicated.

Viral conjunctivitis caused by a herpes infection may be treated with eyedrops containing an antiviral drug. Although other types of viral conjunctivitis cannot be treated, their symptoms usually clear up within 2–3 weeks. Your doctor may prescribe eyedrops or oral antiallergy drugs if you have allergic conjunctivitis.

From the 2010 revision of the Complete Home Medical Guide © Dorling Kindersley Limited.

The subjects, conditions and treatments covered in this encyclopaedia are for information only and may not be covered by your insurance product should you make a claim.

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