What is conjunctivitis?

Conjunctivitis means inflammation of the conjunctiva. The conjunctiva is the thin 'skin' that covers the white part of the eyes and the inside of the eyelids.

Infection is the most common cause. Many bacteria and viruses can cause conjunctivitis.

Allergy is another common cause.

Irritant conjunctivitis sometimes occurs. For example, your conjunctiva may become red and inflamed after getting some shampoo in your eyes. The chlorine in swimming baths is a common cause of mild irritant conjunctivitis.

The rest of this leaflet is about conjunctivitis caused by allergy.

Allergy means that the immune system 'over-reacts' to something which causes inflammation. Causes include the following:

Pollen
Most cases of allergic conjunctivitis occur in the hay fever season. Symptoms tend to last a few weeks each year. This is called 'seasonal conjunctivitis'. Grass pollens tend to cause symptoms in early summer. Various other pollens and moulds may cause symptoms later in the summer. Other symptoms of hay fever may also occur at the same time such as a runny nose and sore throat.

Perennial conjunctivitis
This is a conjunctivitis that persists throughout the year. This is commonly due to an allergy to house dust mite. House dust mite is a tiny insect that lives in every home. It mainly lives in bedrooms and mattresses, as part of the dust. People with perennial conjunctivitis usually also have perennial allergic rhinitis which causes symptoms such as sneezing and a runny nose. Symptoms tend to be worse each morning when you wake up.

Allergies to animals
Coming into contact with some animals can cause a bout of allergic conjunctivitis. (Again, nose symptoms such as sneezing and runny nose often also occur.)

Cosmetics, eye make-up, eye-drops, and other chemicals
In some of these cases, the eye is directly irritated by the chemical. In some cases, the eye becomes sensitised and the chemical causes an allergic response. In this condition the skin on the eyelids also tends to become inflamed.

Giant papillary conjunctivitis
This is uncommon. It is inflammation of the conjunctiva lining the upper eyelid. It occurs in some people who have a 'foreign body' on the eye - most commonly a contact lens. The exact cause of the inflammation is not known - it is possibly an allergic reaction to 'debris' caught behind a lens or to poor lens hygiene. About 1 in 100 contact lens wearers develop this type of conjunctivitis.医学 全在.线提供www.med126.com

What are the symptoms of allergic conjunctivitis?

• Both eyes are usually affected and symptoms tend to develop quickly.
• The eyes are usually itchy, and the whites of the eyes look red or pink.
• A burning feeling may occur, but the eyes are not usually painful.
• The eyelids tend to swell.
• The eyes water more than usual, but do not become too 'gluey' as in infective conjunctivitis.
• Vision is not usually affected.
• In severe cases the conjunctiva under the upper eyelids may swell and look lumpy.

What is the treatment for allergic conjunctivitis?

• Not treating is an option if symptoms are mild.
• Avoid the cause of the allergy if possible. For example, in the hay fever season stay indoors as much as possible, close windows, wear 'wrap around' sunglasses when out, etc.
• Bathing the eyes with a flannel soaked in cold water may ease symptoms for a short while.
• Eye drops that reduce inflammation are often prescribed. There are different types. They usually work well (although they may not work so well for giant papillary conjunctivitis.) You need to use the drops regularly to keep symptoms away until the cause of the allergy goes. Some people find one type works better than another. Therefore, if the first does not work so well, a switch to another may help. If your eyelids are very swollen, it may take several days for the drops to fully ease symptoms.
• Antihistamine tablets. You can take these to ease the general symptoms of hay fever. However, they may not work as well as eye drops to ease the eye symptoms.
• Steroid eye drops are rarely needed or used. Steroids are good at reducing inflammation. However, they should only be used if other treatments fail. They are normally only used under the supervision of an eye specialist as infection and other causes of conjunctivitis need to be definitely ruled out. (Steroids can make some other eye conditions worse.)
• 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. However, your doctor or optometrist will advise if you can wear lenses with certain types of eye drops. If the lens was related to the cause of the allergy (giant papillary conjunctivitis - see above) then improved lens hygiene or a change in lens type may be advised once the symptoms have settled.

It is sometimes difficult for a doctor to tell the difference between allergic and infective conjunctivitis. Particularly in the hay fever season when red, watery eyes are common. Also, some other eye conditions can cause a red eye, and may be mistaken at first for conjunctivitis.

Therefore, see a doctor if any of the following occur.

• Symptoms do not settle within a few days of treatment.
• Symptoms change (for example, light starts to hurt your eyes).
• Pain becomes worse (mild soreness rather than pain is usual with conjunctivitis).
• Spots or blisters develop on the skin next to the eye.
• Your vision becomes affected.