Allergic conjunctivitis is caused by contact with an allergen. An allergen is a substance that triggers a response from the immune system. In people with allergies, the immune system is oversensitive to certain substances. The tendency for allergies is hereditary. Someone who suffers from allergies is likely to have relatives who have allergies, eczema, or asthma.

Pollen, grass, and ragweed are common triggers for allergic conjunctivitis. Examples of other possible causes of allergic conjunctivitis are makeup, perfume, air pollution, and smoke. When a person with allergies comes in contact with an allergen, the body produces the immunoglobulin E antibody. This antibody affects mast cells and triggers the production of histamine. Histamine causes the symptoms of allergies.

There are five categories of allergic conjunctivitis. Seasonal allergic conjunctivitis and perennial allergic conjunctivitis are commonly considered one category. Vernal keratoconjunctivitis (VKC), atopic keratoconjunctivitis, and giant papillary conjunctivitis are the other categories of allergic conjunctivitis. Atopic keratoconjunctivitis is associated with atopic dermatitis, the most common type of eczema. Giant papillary conjunctivitis is often attributed to hypersensitivity to contacts, inflammation from wearing dirty or damaged contacts, or hypersensitivity to the chemicals used to clean contacts.

Allergic conjunctivitis affects both eyes. The signs and symptoms of allergic conjunctivitis are itchiness of the eyes, excessive tearing, and redness. Allergic conjunctivitis should not affect vision. If the person experiences a change in vision, the person should seek immediate medical treatment.

People with allergic conjunctivitis may also experience other symptoms of allergies such as sneezing and watery nasal discharge. Some people with allergic conjunctivitis experience swelling of the conjunctiva. The conjunctiva is the outer membrane of the eye and the underside of the eyelid. Allergic conjunctivitis is not contagious.

A common treatment for allergic conjunctivitis is over-the-counter antihistamines. For severe cases, a doctor may prescribe a mast cell stabilizer, anti-inflammatory eye drops, or steroid treatment. Some people use over-the-counter eye drops to provide relief from the symptoms of allergic pink eye. Decongestants and anti-inflammatory medication is sometimes used as part of treatment for allergic pink eye. Applying warm or cold compresses can help provide some comfort from the itchiness and inflammation of the eyes.

People should avoid wearing contact lenses or eye makeup until the allergic conjunctivitis is gone. Some people with seasonal allergies try to avoid spending excessive amounts of time outdoors when the allergen or pollen levels are high. While many kinds of conjunctivitis typically go away within a two weeks, allergic conjunctivitis may take longer especially if there is any ongoing exposure to the allergen.