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allergic conjunctivitis

Alternative Names 
atopic conjunctivitis, hay fever conjunctivitis

Allergic conjunctivitis is swelling and redness of the membrane that lines the eye. It is caused by exposure to foreign matter. The affected part of the eye is called the conjunctiva. The conjunctiva is the mucous membrane layer that covers the white part of the eye.

What are the signs and symptoms of the condition? 
Usual symptoms include:
  • swelling of the conjunctiva
  • redness
  • itching
  • watery or mucous discharge
The condition can also spread to the eyelids. The eyelids, as well, may become red with thickening, dryness and scaling of the skin.

What are the causes and risks of the condition? 
Pollen is often the cause of the problem. Other vegetable proteins, animal proteins, dust and fungus spores can cause it, too. Sometimes the allergic reaction can happen within minutes. Other times the reaction can be delayed for hours or days. This problem seems to affect people who have other allergy problems. These include eczema, asthma, hay fever or hives.

Other common causes of allergic conjunctivitis are exposure to animal hair, such as cat hair, or feathers.

A less common form of allergic conjunctivitis comes from bacteria on the eyelid or skin. The cause is often the staphylococcus bacteria. This type of allergy may lead to styes, which are pimple-like infections of the glands in the eyelid. It may also cause chalazions, which are blockages of the oil glands in the eyelid. Long-term problems related to allergies in the eye rarely occur. However, if uncontrolled, the problem can spread to other parts of the eye, such as the cornea and the space between the cornea and the iris. This can cause inflammation of the iris, which is the coloured part of the eye.

What can be done to prevent the condition? 
The problem can be prevented by avoiding the material that causes the allergic reaction. Medications or preservatives in eye drops or contact lens solutions might make some people more sensitive. Air filters and air conditioners can reduce dust and allergens in the air. Avoiding dust and animal hair is also important.

How is the condition diagnosed? 
People often think they have allergic conjunctivitis because their eyes are red, itchy or watery. These are also symptoms of hay fever. In more complex cases, the doctor uses a microscope to find signs of an allergy. Tiny bumps on the white part of the eye indicate that an allergy is present. This distinguishes it from bacterial or viral conjunctivitis.

What are the long-term effects of the condition? 
Usually there are no long-term effects when allergic conjunctivitis is managed properly.

What are the risks to others? 
This condition cannot be passed to others.

What are the treatments for the condition? 
Using non-prescription antihistamine eye drops can help some symptoms. In more difficult cases, prescription medications can be used. These are non-steroidal anti-inflammatory drops such as ketorolac, antihistamine eye drops, such as levocabastine, or low-dose steroid drops such as lodoxamide or fluorometholone. Oral antihistamines such as diphenhydramine, loratadine, or fexofenadine may also help. Allergy injections may help desensitise some people. These are given by an allergy specialist. Topical anaesthetic such as alcaine drops should not be used. They damage the cornea. Contact lenses become hard to wear during episodes of allergic conjunctivitis. Sometimes cool compresses will ease symptoms.

What are the side effects of the treatments? 
Antihistamine eye drops should be used sparingly. The drops should be used no more than 4 times a day. If corticosteroid eye drops such as lodoxamide or fluorometholone are used, an eye doctor should be seen periodically. Long-term use can carry the risk of a rise in the pressure inside of the eye. It may also lead to cataracts, or a clouding of the lens of the eye.

What happens after treatment for the condition? 
Since this condition is related to exposure to allergens it is usually chronic, seasonal, and tends to recur. Therefore, at the sign of symptoms, treatment should be started again.

How is the condition monitored? 
Most people are able to monitor their allergic conjunctivitis independently. If medications are used frequently, periodic checkups with a doctor are advised.

Author: William Stevens, MD
Reviewer: eknowhow Medical Review Panel
Editor: Dr John Hearne
Last Updated: 18/09/2004
Potential conflict of interest information for reviewers available on request

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