Conjunctivitis is inflammation of the conjunctiva – the clear membrane that covers the front of the eye and the inner layer of the eyelids. Allergic conjunctivitis is caused by an allergic reaction.
Symptoms and signs of allergic conjunctivitis include:
- red or pink eyes – usually both eyes are affected;
- itchy eyes or burning eyes and surrounding skin;
- sensation of grittiness in the eyes;
- watery discharge from the eyes (excess tears);
- discomfort in bright light (photophobia); and
- swollen (puffy), red eyelids.
Symptoms of allergic conjunctivitis may occur all year long (perennial allergic conjunctivitis) or may be seasonal, depending on what you are allergic to.
People with allergic conjunctivitis also commonly report symptoms of other allergic conditions, including:
- hay fever (itchy nose, sneezing, watery nasal discharge); and
- eczema (red, itchy, scaly skin).
Allergic conjunctivitis often occurs in people who have atopy – an inherited tendency to develop allergic conditions (including hay fever, eczema and asthma).
Typical substances that can cause allergic conjunctivitis include:
- dust mites;
- animal dander (skin scales or flakes from the hair or feathers of animals);
- pollen; and
- mould spores.
When you are exposed to a substance that you are allergic to (an allergen), your immune system responds by producing antibodies called IgE antibodies. These antibodies trigger mast cells (found in the mucous lining of your eyes, respiratory tract and skin) to release several chemicals, including histamine. The amount of histamine that is released determines the severity of the allergic reaction.
The diagnosis can usually be made based on a description of symptoms and an eye examination. Your doctor may also recommend tests to determine what substances you are allergic to.
Treatment for allergic conjunctivitis will depend on its severity.
Medicines that can be used to control the allergic reaction include:
- antihistamines (either as eye drops or taken by mouth); and
- mast cell stabilisers (eye drops).
There are some eye drops that have both antihistamine and mast cell stabilising effects.
Medicines that can be used to control inflammation of the eye include:
- vasoconstrictor, or decongestant, eye drops;
- non-steroidal anti-inflammatory drops; and
- corticosteroid eye drops.
There are some eye drops available that contain a combination of both antihistamine and decongestant.
If the cause of your allergic conjunctivitis has been determined, attempts should be made to avoid the allergen as much as possible to improve symptoms. However, avoiding allergens isn't easy for everyone.
Frequent hand washing and avoiding rubbing your eyes may help prevent airborne allergens being transferred to the eyes.
Severe allergic conjunctivitis that isn't helped by other treatments may benefit from specific allergen immunotherapy (desensitisation). This involves giving increasing doses of the allergen with the aim of regulating your immune system to reduce your body's reaction to that particular allergen.
There are a number of self-help measures you can take to improve the symptoms of allergic conjunctivitis, including:
- applying a cold compress to the eyes;
- washing out your eyes with saline or cold water;
- using an over-the-counter lubricant medicine for the eyes; and
- removing contact lenses (if you wear them) until symptoms have resolved.