Allergic Conjunctivitis

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.

Perennial conjunctivitis

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.

Contact conjunctivitis

Some people become sensitised 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.

What are the symptoms of allergic conjunctivitis?

  • • Both eyes are usually affected and symptoms tend to develop quickly.
  • • The eyes are usually itchy and gritty.
  • • The skin on the inside of the eyelids looks red and sore.
  • • The whites of the eyes look red or pink.
  • • A burning feeling may occur, although the eyes are not usually painful.
  • • The eyelids tend to swell.
  • • The eyes water more than usual; however, they do not become too gluey or sticky.
  • • Vision is not affected.
  • • In severe cases the conjunctiva under the upper eyelids may swell and look lumpy.

Are there any possible complications?

Seasonal and perennial conjunctivitis can be unpleasant; however, complications do not usually occur. Contact dermatoconjunctivitis and giant papillary conjunctivitis occasionally cause inflammation and ulceration of the cornea (a condition called keratitis). This can have a long-term effect on vision if left untreated.

What is the treatment for allergic conjunctivitis?

General measures

The following can be useful whatever the cause of the allergic conjunctivitis:

  • • Try not to rub your eyes, as this can cause more inflammation.
  • • Cold compresses
  • • Avoid the cause of the allergy, if possible. Close windows, drive with windows shut and internal air circulation on in your car, and by wear wraparound sunglasses when out.
  • • If you use contact lenses: in general, do not wear lenses until symptoms have gone, and for 24 hours after the last dose of any eye drop or ointment.

Treatment for seasonal, perennial and animal-related conjunctivitis

In addition to the general measures described above:

Eye drops