Allergic conjunctivitis causes red, watery, itchy or gritty eyes. The condition is not usually painful and does not make eyes sensitive to light. It does not affect vision. The most common cause is an allergy to pollen in the hay fever season. Other causes are allergies to house dust mite, cosmetics, and problems with contact lenses, although these are less common. Eye drops usually ease symptoms.
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. It is made up of layers of specially adapted see-through (transparent) cells.
What causes conjunctivitis?
Conjunctivitis is usually due to allergy, infection or irritation of the conjunctiva.
Allergy is a very common cause.
Infection is the most common cause and, in addition to itch, redness and grittiness, there is usually a sticky discharge. Many germs (bacteria and viruses) can cause conjunctivitis. See separate leaflet called Infective Conjunctivitis for more details.
Irritant conjunctivitis is something most of us have experienced occasionally. For example, your conjunctiva may become red and inflamed after getting shampoo in your eyes, or after you rub your eyes when chopping chillies. The chlorine in swimming baths is another common cause. Also, in the days when smoking was allowed in bars, many people developed irritant conjunctivitis from cigarette smoke.
This rest of this leaflet is about conjunctivitis caused by an allergy.
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 and occur in the hay fever season. Symptoms tend to last a few weeks each year and may vary with the pollen count. This is a measure of the amount of pollen in the air each day. The pollen count is often published in the press and in online weather forecasts.
Different people are sensitive to different groups of pollens. Grass pollens tend to cause symptoms in early summer, usually from April through to July in the UK. Tree pollens may cause symptoms as early as February or March or as late as September, depending on when the tree species involved shed their pollen. Various other 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 (perennial means through the year). This is most commonly due to an allergy to house dust mite. House dust mite is a tiny insect-like creature that lives in every home. It mainly lives in bedrooms, carpets and mattresses, as part of the dust. 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 is an inflammation of the conjunctiva lining the upper eyelid. It occurs in some people who have a small object on the eye - most commonly, a contact lens. 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 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?
The following can be useful whatever the cause of the allergic conjunctivitis:
- 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. However, your doctor or optician (optometrist) will advise if you can wear lenses with certain types of drops.
- Try not to rub your eyes, as this can cause more inflammation.
- Bathing the eyes with a flannel soaked in cold water or with an over-the-counter 'eye bath' may ease symptoms.
- Avoid the cause of the allergy, if possible. For example, if you have seasonal conjunctivitis then during the hay fever season try to avoid pollen by staying indoors as much as possible. Close windows, drive with windows shut and internal air circulation on in your car, and by wear wraparound sunglasses when out.
Treatment for seasonal, perennial and animal-related conjunctivitis
In addition to the general measures described above:
If symptoms are mild, no treatment may be needed.
Eye drops that reduce the allergic reaction are often prescribed. (Tablets may also be prescribed and, in the past, injections have been used.)
The most commonly used eye drops are antihistamine eye drops and mast cell stabiliser eye drops. (Mast cells and histamine are both part of the body's allergic reaction. The eye drops counter their effects.) Eye drops usually work well. You need to use them regularly to keep symptoms away until the cause of the allergy goes away (if it does). Some people find one product 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 ease symptoms fully.
- Antihistamine eye drops - eg, azelastine eye drops: these are usually needed only twice a day. They have few side-effects and can be very effective in reducing symptoms.
- Mast cell stabiliser eye drops - eg, sodium cromoglycate drops: these have been in use for many years. They are very effective and relatively free from side-effects. They need to be used frequently, as they are shorter-acting: four times a day or more.
- Combination anti-allergy drops - which contain antazoline and xylometazoline: antazoline is an antihistamine like azelastine; xylometazoline is a vasoconstrictor. Vasoconstrictors are medicines which narrow the tiny blood vessels in the surface of the eye to stop them from carrying so many allergy-creating chemicals to the site of irritation. These combination drops are not suitable for everyone. For instance, children aged under 12 years and people with raised pressure in the eye (glaucoma) should not use them. Your doctor or pharmacist can advise if they are safe for you.
- Antihistamine tablets - eg, chlorphenamine or loratadine tablets: these are taken to try to generally lower the allergic response in your body. They tend not to be highly effective for eyes which are very irritated; however, they may help with other symptoms of hay fever. Antihistamines can cause drowsiness. Therefore, care is needed if taking them when operating heavy machinery or when driving :
- Modern antihistamines such as loratadine are taken once daily and they tend to cause less drowsiness. However, their effect on your sleepiness is never certain until you have tried them.
- Chlorphenamine (which is licensed for use even in small children) is short-acting and usually needs to be taken four times a day. However, this antihistamine is prone to cause drowsiness.
- Steroid eye drops - eg, betamethasone eye drops: steroid drops are very effective in eye irritation. They calm down irritation and inflammation quickly. However, if infection is present (especially viral infection) they can rapidly make it severe. They can also cause glaucoma. Steroid drops should therefore only be used if other treatments fail. They are normally only used under the supervision of an eye specialist (ophthalmologist). Your GP will be reluctant to prescribe them.
- Steroid injections - eg, triamcinolone (Kenalog®): years ago it was common for patients to ask their doctor for a steroid injection once per hay fever 'season'. This could be quite effective in reducing the symptoms of hay fever. However, the side-effects and consequences of using injectable steroids every year are considerable. Steroids reduce immunity, cause weight gain and can markedly thin the bones. Thinning of the bones has enormous consequences in later life, when it can lead to fractures of the hip and spine. Doctors do not feel that these risks are justified to treat hay fever, even though its symptoms can be very irritating and distressing.
- Steroid tablets - these are occasionally used for 3-5 days when symptoms are severe: steroid tablets work well but regular or longer courses are not advised because of possible side-effects with long-term use. The side-effects of repeated courses of oral steroids include increased appetite, weight gain, suppression of the immune system (which is why they are used, but which is not good if you need to fight infection) and thinning of the bones.
Note: tell your doctor or pharmacist if you are pregnant or breast-feeding, as some treatments (including some eye drops) may not be advised.
Eye drops and contact lenses
Most drops contain preservatives. However, in some cases preservative-free versions are available, as the preservatives may also cause eye irritation or allergy! Soft contact lenses should not be worn whilst the drops are being used, as the preservatives can be absorbed into the lenses and can further irritate the eyes.
Treatment for giant papillary conjunctivitis
A problem with contact lenses is the main cause of this condition. Treatment is generally to remove contact lenses until the symptoms clear. Improved lens hygiene or a change in lens type may be needed to stop the problem returning. Antihistamine eye drops or mast cell stabiliser eye drops (described above) may also help to ease symptoms before the lenses are tried again..
Treatment for contact conjunctivitis
Treatment is to avoid whatever caused the reaction. When caused by a cosmetic, you should let symptoms go completely before trying an alternative product. Mascara should be changed for a fresh bottle every three months in any case, on hygiene grounds. However, it may be necessary to change brand or type of eye make-up. Make-up which drops tiny fibres into the eyes, such as lash-lengthening mascaras, is a common cause. Lash-building and lash-thickening mascaras are often the culprits.
Some cases are caused by an allergy to a particular eye drop used for another eye disease. Glaucoma drops can commonly have this effect, as can the drops sold by pharmacists for lengthening eyelashes (these are actually a type of glaucoma medication). In the first situation you may need a specialist's advice as to what alternative eye drops may be suitable for the condition. In the second you may have to forget about lengthening eyelashes, or consider eyelash extensions (which need to be renewed every three to four weeks).
The general measures described earlier may help to soothe the eye until symptoms resolve. Antihistamine eye drops or mast cell stabiliser eye drops (described above) do not work in this type of conjunctivitis.
What should I look out for?
It is sometimes difficult for a doctor to tell the difference between allergic and infective conjunctivitis. This is particularly so in the hay fever season when red, watery eyes are common. Allergic conjunctivitis and bacterial conjunctivitis usually affect both eyes:
- In allergic conjunctivitis both eyes tend to be equally affected at the same time.
- In bacterial conjunctivitis the condition tends to spread from one eye to the other.
If only one eye is red then it is very unlikely to be due to allergic conjunctivitis.
Many other eye conditions can cause one or both of the eyes to be red, and these may be mistaken at first for conjunctivitis. They include inflammatory conditions affecting the inside of the eye, shingles, iritis and ulceration of the eye (although all these conditions tend to cause blurring or reduction of vision, together with pain).
You should see a doctor if you are uncertain what is causing your symptoms and the symptoms do not settle within a few days. Also, see a doctor urgently if any of the following occur:
- Your symptoms change (for example, light starts to hurt your eyes).
- You have pain in the eye (mild soreness rather than pain is usual with conjunctivitis).
- Spots or blisters develop on the skin next to the eye, or on your eyelid or nose.
- Your vision is reduced.
- The eye becomes very red - in particular, if it is on one side only.
Further reading and references
; Topical treatments for seasonal allergic conjunctivitis: systematic review and meta-analysis of efficacy and effectiveness. Br J Gen Pract. 2004 Jun54(503):451-6.
; NICE CKS, August 2012 (UK access only)
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