WHAT CAUSES ALLERGIC CONJUNCTIVITIS?
Allergy means that the immune system overreacts to something to which it has become sensitive. Symptoms of increased immune activity in the eyes include redness, wateriness and itching. These are part of the body’s defence mechanism to things it sees as foreign and harmful. Causes include the following:
SEASONAL CONJUNCTIVITIS DUE TO POLLENS AND MOULDS
Seasonal conjunctivitis occurs at the same time each year. Most cases are due to pollen. Symptoms tend to last a few weeks each year and may vary with the pollen count. Various pollens and moulds cause symptoms later in the summer.
If you have seasonal conjunctivitis you may also have other symptoms of hay fever, such as a runny nose and sore throat.
This is a conjunctivitis that persists throughout the year. This is most commonly due to an allergy to house dust mite. People with perennial conjunctivitis usually also have perennial allergic rhinitis (this causes symptoms such as sneezing and a runny nose). Symptoms tend to be worse each morning when you first wake.
ALLERGIES TO ANIMALS
Coming into contact with some animals can cause allergic conjunctivitis. This is usually due to allergy to fur or hair.
GIANT PAPILLARY CONJUNCTIVITIS
This is uncommon. It affects about 1 in 100 wearers of contact lenses. The exact cause of the inflammation is unclear – it is possibly an allergic reaction to debris caught behind a lens or to poor lens hygiene (not being careful enough with managing your lenses). It also sometimes develops after eye surgery.
Some people become sensitized to cosmetics, make-up, eye drops or other chemicals that come into contact with the conjunctiva. This then causes an allergic response and symptoms of allergic conjunctivitis. In this condition the skin on the eyelids may also become inflamed. It is then called contact dermatoconjunctivitis.