ConjunctivitisSee all parts of this guide Hide guide parts
Conjunctivitis is a common condition that causes redness and inflammation of the thin layer of tissue that covers the front of the eye (the conjunctiva).
People often refer to conjunctivitis as red eye.
Other symptoms of conjunctivitis include itchiness and watering of the eyes, and sometimes a sticky coating on the eyelashes (if it's caused by an allergy).
Read more about the symptoms of conjunctivitis
Conjunctivitis can affect one eye at first, but usually affects both eyes after a few hours.
What causes conjunctivitis?
The conjunctiva can become inflamed as a result of:
- a bacterial or viral infection – this is known as infective conjunctivitis
- an allergic reaction to a substance such as pollen or dust mites – this is known as allergic conjunctivitis
- the eye coming into contact with things that can irritate the conjunctiva, such as shampoo or chlorinated water, or a loose eyelash rubbing against the eye – this is known as irritant conjunctivitis
Read more about the causes of conjunctivitis
Treatment isn't usually needed for conjunctivitis, because the symptoms often clear up within a couple of weeks. If treatment is needed, the type of treatment will depend on the cause. In severe cases, antibiotic eye drops can be used to clear the infection.
Irritant conjunctivitis will clear up as soon as whatever is causing it is removed.
Allergic conjunctivitis can usually be treated with anti-allergy medications such as antihistamines. If possible, you should avoid the substance that triggered the allergy.
It's best not to wear contact lenses until the symptoms have cleared up. Any sticky or crusty coating on the eyelids or lashes can be cleansed with cotton wool and water.
Washing your hands regularly and not sharing pillows or towels will help prevent it spreading.
Read more about treating conjunctivitis
Immediate action required: Speak to your optician immediately if:
- eye pain
- sensitivity to light (photophobia)
- disturbed vision
- intense redness in one eye or both eyes
- a newborn baby with conjunctivitis
Work and school
Public Health Scotland (PHS) advises that you don't need to stay away from work or school if you or your child has conjunctivitis, unless you (or they) are feeling particularly unwell.
If there are a number of conjunctivitis cases at your child's school or nursery, you may be advised to keep them away until their infection has cleared up.
Generally, adults who work in close contact with others, or share equipment such as phones and computers, shouldn't return to work until the discharge has cleared up.
Conjunctivitis can be a frustrating condition – particularly allergic conjunctivitis – but in most cases it doesn't pose a serious threat to health.
Complications of conjunctivitis are rare, but when they do occur they can be serious and include:
- a severe case of allergic conjunctivitis can lead to scarring in the eye
- in cases of infective conjunctivitis, the infection can spread to other areas of the body, triggering more serious secondary infections, such as meningitis
Read more about the complications of conjunctivitis
Symptoms of conjunctivitis
The symptoms of conjunctivitis will depend on what's causing the condition.
However, the 2 main symptoms are usually:
- eye redness – as a result of the inflammation and widening of the tiny blood vessels in the conjunctiva (the thin layer of cells covering the front of the eyes)
- a discharge – the conjunctiva contains thousands of cells that produce mucus and tiny glands that produce tears – inflammation causes the glands to become overactive, so that they produce more water and mucus
Only one eye tends to be affected at first, but symptoms usually affect both eyes within a few hours.
If you have infective conjunctivitis, you may also have:
- a burning sensation in your eyes
- a feeling of grit in your eyes
- a sticky coating on the eyelashes – usually when you first wake up in the morning
- an enlarged lymph node (gland) in front of the ear
You may have itchy eyes if you have allergic conjunctivitis.
The pattern of symptoms for allergic conjunctivitis depends on the substance you're allergic to.
Allergies to pollen (hay fever) occur during certain parts of the year. You can have an allergy to:
- tree pollen, released during spring
- grass pollen, released during the end of spring and beginning of summer
- weed pollen, released any time from early spring to late autumn
It's highly likely that the pollen will also cause other symptoms, such as sneezing and a runny or blocked nose.
Allergies to dust mites or animal fur cause symptoms throughout the year. Both eyes are usually affected and you may find the symptoms worse in the morning.
Some people develop an allergy to eye drops. This is known as contact dermatoconjunctivitis and it can also affect your eyelids, causing them to become dry and sore.
Some people are allergic to wearing contact lenses, which is known as giant papillary conjunctivitis. The symptoms progress much more slowly and you may also develop small spots on the inside of your upper eyelids. This type of conjunctivitis carries a high risk of complications, so you need to seek medical advice as soon as possible.
When to seek medical advice
Most cases of conjunctivitis aren't a cause for concern, but you should contact your optician if you think you have it, particularly if you think it's related to wearing contact lenses.
Your optician can check whether there's a more serious underlying cause of your symptoms.
When to seek immediate medical advice
The following symptoms could be the sign of a more serious eye condition:
- pain in your eyes
- sensitivity to light (photophobia)
- disturbed vision
- intense redness in one eye or both eyes
Contact your optician immediately if you experience any of these symptoms. If this isn't possible, visit your nearest accident and emergency (A&E) department.
Causes of conjunctivitis
Conjunctivitis is a condition that occurs when the conjunctiva (a thin layer of cells covering the front of your eyes) becomes inflamed.
The 3 most common causes of this inflammation are:
- infection (infective conjunctivitis)
- an allergic reaction (allergic conjunctivitis)
- something irritating the conjunctiva, such as a loose eyelash (irritant conjunctivitis)
These are discussed in more detail below.
Eye infections are most commonly caused by:
- bacteria – for example, the strains of bacteria that often cause lung and ear infections
- a virus – most commonly an adenovirus that may also cause a sore throat and high temperature (fever)
- sexually transmitted infections (STIs) – such as chlamydia or gonorrhoea
Viral conjunctivitis causes a watery discharge, while the discharge from bacterial conjunctivitis contains pus. An eye swab can also determine the cause of the infection (read more about diagnosing conjunctivitis).
Spreading the infection
You're more likely to develop infective conjunctivitis if you've been in close contact with someone who's already infected with it.
It's therefore very important to wash your hands thoroughly after coming into contact with anyone who has infective conjunctivitis. You should also avoid sharing pillows or towels with anyone with the infection.
You may be more at risk of getting infective conjunctivitis if:
- you're old or young – it's more common in children and the elderly, possibly because children come into contact with more infections at school, and elderly people may have a weaker immune system
- you've recently had an upper respiratory tract infection – such as a cold
- you have diabetes or another condition that weakens your immune system – as you may be more vulnerable to infections
- you're taking corticosteroids (steroids) – which can weaken your immune system
- you have blepharitis (inflammation of the rims of the eyelids) – which can be caused by a bacterial infection and may lead to conjunctivitis
- you've been in a crowded place – such as a busy train
Allergic conjunctivitis is caused when your eyes come into contact with an allergen (a particular substance that causes your immune system to react abnormally). This is known as an allergic reaction.
There are 4 main types of allergic conjunctivitis:
- seasonal allergic conjunctivitis
- perennial allergic conjunctivitis
- contact dermatoconjunctivitis
- giant papillary conjunctivitis
Seasonal and perennial conjunctivitis
Seasonal and perennial allergic conjunctivitis are usually caused by:
- pollen from grass, trees or flowers
- dust mites
- flakes of dead animal skin
These types of conjunctivitis are more common in people who also have other allergies, such as asthma, and often occur with allergic rhinitis.
Contact dermatoconjunctivitis is usually caused by eye drops, but it can also be caused by make-up or chemicals.
Giant papillary conjunctivitis
Giant papillary conjunctivitis is caused by:
- contact lenses
- stitches used in eye surgery
- a prostheses (artificial) part of the eye that's fitted during eye surgery
Giant papillary conjunctivitis is estimated to affect around 1% to 5% of people who use soft contact lenses and 1% of people who use hard contact lenses.
Irritant conjunctivitis can have a wide range of potential causes. Some common causes include:
- chlorinated water used in swimming pools
- a stray eyelash rubbing against the conjunctiva
- smoke or fumes
Your optician should be able to diagnose conjunctivitis by asking about your symptoms and examining your eyes.
Describing how your conjunctivitis started can help your optician diagnose which type it is and decide whether it needs to be treated.
The most common symptoms of infective conjunctivitis are sticky, red and watery eyes. However, infective conjunctivitis can sometimes be confused with other types of conjunctivitis, which are treated differently.
Your optician may suggest further tests, such as a swab test, if your conjunctivitis hasn't responded to treatment, or to help decide what treatment to use.
A swab looks similar to a cotton bud. It's used to collect a small sample of mucus from your infected eye, which is sent to a laboratory to find out the cause of your conjunctivitis.
If your symptoms are severe or don't respond to treatment, you may need to see an eye specialist (ophthalmologist).
Most cases of conjunctivitis clear up within 1 to 2 weeks without needing any medical treatment. In some cases, it can last for longer than 2 weeks, which is known as persistent infective conjunctivitis.
If you have any unusual symptoms, such as severe pain, blurred vision or sensitivity to light, it may mean that you have a more serious condition.
If you have any of these symptoms, it's very important to seek medical assistance immediately, either by contacting your optician or going to your nearest hospital.
Other more serious conditions include:
- acute glaucoma – a rare form of glaucoma that causes a painful build-up of pressure in your eye
- keratitis – where the cornea (the clear layer at the front of your eye) becomes swollen and develops open sores
- iritis – a type of uveitis (swelling of the middle layer of your eye) that causes pain, headaches and watery eyes
Contact your optician straight away if you think your baby may have infective conjunctivitis (also called neonatal conjunctivitis).
If this isn't possible, call NHS 24's '111' service or your local out-of-hours service. Your optician will examine your baby closely to see if they have sticky eyes or infective conjunctivitis.
All newborn babies with infective conjunctivitis must be referred to an eye specialist straight away for treatment.
Read more about the symptoms of infective conjunctivitis
The recommended treatment for conjunctivitis will depend on whether it's caused by infection, an allergic reaction or an irritant, such as a stray eyelash.
Most cases of infective conjunctivitis don't need medical treatment and clear up in 1 to 2 weeks.
There are several ways you can treat infective conjunctivitis at home:
- remove your contact lenses – if you wear contact lenses, take them out until all the symptoms of the infection have gone; don't re-use old lenses after the infection has gone because they could be a potential source of re-infection; always use new lenses, solutions and cases after an infection
- use lubricant eye drops – these are available over the counter at pharmacies or they may be prescribed for you; they may help ease any soreness and stickiness in your eyes; always follow the manufacturer’s instructions
- gently clean away sticky discharge from your eyelids and lashes using cotton wool soaked in water
- wash your hands regularly – this is particularly important after touching your eyes and will stop the infection spreading to others
Antibiotics aren't usually prescribed for infective conjunctivitis because it usually clears up by itself and there's a very low risk of complications for untreated conjunctivitis.
However, if the infection is particularly severe or it has lasted for more than 2 weeks, you may be prescribed antibiotics. Some schools or playgroups may insist that a child is treated with antibiotics before they can return, although this is rare.
Chloramphenicol and fusidic acid are the two main types of antibiotics that may be prescribed.
Chloramphenicol is usually the first choice of antibiotic and comes in the form of eye drops. It's available without a prescription from pharmacies to treat bacterial conjunctivitis.
Chloramphenicol needs to be used carefully to get the best results, so make sure you follow the advice of your pharmacist about how and when to use it, or check the patient information leaflet that comes with the medication so you know how to use it properly.
If eye drops aren't suitable for you, you may be prescribed the antibiotic as an eye ointment instead.
Fusidic acid may be prescribed if chloramphenicol isn't suitable for you. It's often better for children and elderly people because it doesn't need to be used as often. It's also the preferred treatment for pregnant women.
Like chloramphenicol, fusidic acid comes in the form of eye drops and should be used as advised by your doctor or as described in the instructions that come with the medication.
Eye drops can briefly cause blurred vision. Avoid driving or operating machinery straight after using eye drops.
Chloramphenicol and fusidic acid can also cause other side effects, such as a slight stinging or burning sensation in your eye, although this shouldn't last long.
It's very important to go back to your optician if you still have symptoms after 2 weeks. You should also contact your optician immediately if you experience any of the following symptoms:
- eye pain
- sensitivity to light (photophobia)
- loss of vision
- intense redness in one eye or both eyes
Your optician may recommend that you're tested for sexually transmitted infections (STIs). Some STIs, such as chlamydia, can cause infective conjunctivitis. If this is the case, your symptoms may last for several months.
Your treatment will depend on the type of allergic conjunctivitis you have.
The 4 main types of allergic conjunctivitis are:
- seasonal conjunctivitis – typically caused by an allergy to pollen
- perennial conjunctivitis – usually caused by an allergy to dust mites or pets
- contact dermatoconjunctivitis – usually caused by an allergy to eye drops or cosmetics
- giant papillary conjunctivitis – usually caused by an allergy to contact lenses
Whatever the cause, you'll find that some self-help methods can ease your symptoms.
If you have allergic conjunctivitis, you can follow the guidelines below to treat your condition at home:
- if you wear contact lenses, take them out until all the signs and symptoms of the conjunctivitis have gone
- don't rub your eyes, even though they may be itchy – rubbing your eyes can make your symptoms worse
- place a cool compress over your eyes – wetting a flannel with cool water and holding it over your eyes will help ease your symptoms
- avoid exposure to the allergen, if possible
Seasonal and perennial allergic conjunctivitis
If you have seasonal or perennial conjunctivitis, you may be prescribed the following medicines:
- mast cell stabilisers
If allergic conjunctivitis needs rapid relief, your optician will probably prescribe a medicine known as an antihistamine.
Antihistamines work by blocking the action of the chemical histamine, which the body releases when it thinks it's under attack from an allergen. This prevents the symptoms of the allergic reaction occurring.
Antihistamine eye drops
You may be prescribed antihistamine eye drops, such as:
- azelastine (not suitable for children under four years of age)
- emedastine (not suitable for children under three years of age)
- ketotifen (not suitable for children under three years of age)
- antazoline with xylometazoline (Otrivine-Antistin, not suitable for children under 12 years of age)
Antazoline with xylometazoline (Otrivine-Antistin) is also available over the counter from pharmacies without prescription. Always follow the manufacturer’s instructions.
If you're pregnant or breastfeeding, some antihistamine eye drops may not be suitable. Speak to your optician for advice.
You may be prescribed an antihistamine such as:
You'll usually only have to take an antihistamine once a day.
If possible, oral antihistamines shouldn't be taken if you're pregnant or breastfeeding. Speak to your optician for advice.
Although new antihistamines shouldn't make you drowsy, they may still have a sedating effect. This is more likely if you take high doses or drink alcohol while you're taking antihistamines.
Mast cell stabilisers
Mast cell stabilisers are an alternative type of medicine. Unlike antihistamines, they won't provide rapid symptom relief, but they are better at controlling your symptoms over a longer period of time.
It may take several weeks to feel the effects of a mast cell stabiliser, so you may also be prescribed an antihistamine to take at the same time.
Mast cell stabilisers that are commonly prescribed in the form of eye drops include:
- nedocromil sodium
- sodium cromoglicate
If your symptoms of allergic conjunctivitis are particularly severe, you may be prescribed a short course of topical corticosteroids (a cream, gel or ointment). However, these aren't usually prescribed unless absolutely necessary.
Giant papillary conjunctivitis
As giant papillary conjunctivitis is usually caused by contact lenses, the symptoms often clear up after you stop wearing them. The spots that form on the inside of your upper eyelid may last slightly longer.
If you develop giant papillary conjunctivitis as a result of recent eye surgery, you'll be immediately referred to an ophthalmologist. This is so that your eyes can be carefully monitored and the most effective treatment given.
Most cases of irritant conjunctivitis don't need any treatment, as the condition should clear up once the irritant is removed from the eye.
An exception to this is if your eyes were exposed to harmful substances such as bleach or acid. This is usually regarded as a medical emergency and you'll need to be admitted to hospital so your eyes can be washed out with saline solution.
Complications of conjunctivitis
Complications of conjunctivitis depend on whether the condition is an infection (infective conjunctivitis) or an allergic reaction (allergic conjunctivitis).
If conjunctivitis has been caused by a sexually transmitted infection (STI), particularly chlamydia, the infection may last several months, rather than weeks.
Infective conjunctivitis caused by any type of bacteria can result in a number of complications, particularly in babies born prematurely (before week 37 of pregnancy).
Possible complications include:
- meningitis – an infection of the meninges (the protective layer of cells surrounding the brain and spinal cord)
- cellulitis – an infection of the deep layer of skin and tissue that causes the skin on the surface to become sore and inflamed. It's usually easily treated with antibiotics
- septicaemia – more commonly known as blood poisoning, septicaemia occurs when bacteria get into the bloodstream and attack the body's tissues
- otitis media – a short-term ear infection that affects around one in four children who have had infective conjunctivitis caused by the haemophilus influenzae bacteria
In newborn babies (neonates) up to 28 days old, infective conjunctivitis can lead to a severe and rapidly progressive eye infection. If this isn't treated, it can cause permanent damage to the child’s vision.
If your newborn baby is found to have infective conjunctivitis, they'll immediately be referred for specialist assessment and treatment. Their condition will be closely monitored. Complications of infective conjunctivitis are rare and most babies make a full recovery.
After having infective conjunctivitis caused by chlamydia, around 1 in 5 babies may develop pneumonia. This is a potentially life-threatening condition in young babies and may need treatment in hospital.
If your conjunctivitis is caused by an allergic reaction to pollen, dust mites or similar (seasonal and perennial allergic conjunctivitis), it's very rare to experience any serious complications.
However, you may find your reoccurring symptoms frustrating. For example, if your conjunctivitis is caused by pollen, you may find it difficult to go outside during the spring and summer months without triggering your symptoms.
This type of allergic conjunctivitis can affect your daily life and could make it difficult for you to concentrate at work or school, particularly if your eyes are severely irritated. Although this can affect your quality of life, it shouldn't cause any long-term health problems.
Punctate epithelial keratitis
Some types of conjunctivitis can cause a condition called keratitis. Keratitis is where your cornea (the front of your eye) becomes swollen.
This can be painful and make your eyes sensitive to light (photophobia). Ulcers sometimes form on the cornea. If the ulcers scar your cornea, your vision may be permanently damaged.
If you experience any unusual symptoms, contact your optician immediately or visit your nearest accident and emergency (A&E) department.
27 February 2023
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