For the last year, my daughter has suffered from what appears to be conjunctivitis, sometimes in just one eye and other times in both eyes. Despite the use of antibiotic cream, it has not cleared up. She does notice that her problems develop more often when she visits a house where cats are present. Do you have any advice?

L.

Conjunctivitis is a medical term used to describe a variety of conditions in which the white part of the eye becomes inflamed. There are many types of conjunctivitis, including those caused by bacteria, viruses and allergies.

Viruses are responsible for the condition commonly known as "pink eye," or viral conjunctivitis. This highly contagious infection causes severe eye redness and itching that lasts for a week to 10 days. Certain anti-inflammatory medications can shorten the course of symptoms, and this condition rarely causes any long-term problems. After 10 days, patients are generally no longer infectious. Viral conjunctivitis never lasts for more than a few weeks.

Bacterial conjunctivitis also causes red eyes, but it is distinguished from viral conjunctivitis by a thick yellowish or greenish discharge. With proper antibiotic treatment, this condition usually disappears over a few days. It also only rarely has any lasting effect on a patient's vision.

Given what you have told me, your daughter would seem to be suffering from allergic conjunctivitis. In this condition, the eye becomes red and itchy for a short period of time (hours to days). The symptoms occur when the patient is exposed to something that may trigger ocular allergies, such as animals, pollen or fibers. Cats may be more likely than dogs to cause such reactions because they groom themselves more, causing more of the allergy-causing proteins (allergens) in their skin and saliva to be released into the air. It is not surprising that an antibiotic cream would not relieve allergic conjunctivitis, because germs do not cause this condition. The best treatment for allergic conjunctivitis is to avoid allergens -- which in your daughter's case may involve steering clear of cats. If that is not possible, antihistamine drugs and prescription allergy eyedrops often help reduce the redness and itching.