Conjunctivitis (Pink Eye): Types, Contagiousness and Treatment

Conjunctivitis is inflammation of the conjunctiva, the thin, transparent membrane that covers the white of the eye and lines the inside of the eyelids. When it becomes inflamed, the small blood vessels in the membrane widen and the eye looks pink or red, which is why the condition is widely known as pink eye. It is one of the most common eye problems in both children and adults and a frequent reason for visits to family doctors and pharmacies.

Most cases are mild and clear up on their own within one to two weeks, but the cause matters: viral and bacterial conjunctivitis can spread easily, allergic conjunctivitis is not contagious at all, and a few forms, especially in newborns and contact lens wearers, need prompt medical treatment. This guide helps you understand the different types, how to reduce the risk of spreading infection, what treatments actually help and which warning signs mean that a red eye is something more serious.

The three main types at a glance

In practice, the types overlap and can be hard to distinguish, even for clinicians, so if you are unsure, it is reasonable to seek advice from a pharmacist, optometrist or doctor.

Viral conjunctivitis

Viruses, most often adenoviruses, cause the majority of infective conjunctivitis in adults. It frequently accompanies or follows a cold. The eye becomes red, watery and gritty, and the other eye often becomes involved a few days later. A tender lymph node in front of the ear is a typical sign. Symptoms often worsen for the first several days before improving, and the illness can last one to three weeks.

A more severe form, epidemic keratoconjunctivitis, can spread rapidly in families, schools and workplaces and can cause small opacities in the cornea that blur vision and light sensitivity for weeks. Other viruses, including herpes simplex and herpes zoster (shingles), can also infect the eye; these need specific antiviral treatment and should be assessed by a doctor, especially if there are blisters on the eyelid or skin around the eye.

Bacterial conjunctivitis

Bacterial conjunctivitis typically produces a thicker, sticky yellow or green discharge, and the lids may be glued together on waking. It is particularly common in young children. In most healthy people it clears up without treatment within about a week. Antibiotic eye drops or ointment can shorten the illness slightly and may be needed for school or nursery attendance in some places, but they are not always necessary.

Some bacteria cause more serious infections. Conjunctivitis caused by sexually transmitted infections such as gonorrhoea or chlamydia can cause heavy discharge or a persistent, low-grade conjunctivitis lasting weeks. Gonococcal infection can progress quickly and damage the cornea, so a sudden, very heavy pus-like discharge needs urgent medical attention.

Allergic conjunctivitis

Allergic conjunctivitis happens when the conjunctiva reacts to allergens such as pollen, house dust mites, pet dander or mould. Itching is the dominant symptom, both eyes are usually affected and there is often sneezing or a runny nose. It is not contagious. Seasonal forms flare during pollen season, while perennial forms continue all year. Treatment focuses on avoiding triggers and using anti-allergy eye drops. For a detailed look at allergic eye disease, including more severe forms, see our eye allergies guide.

Other causes

• Irritants: smoke, chlorine in swimming pools, shampoos or a foreign body can cause irritant conjunctivitis. Our article on swimming and your eyes covers pool-related redness.
• Chemical splashes: an emergency requiring immediate rinsing with plenty of clean water and urgent assessment.
• Contact lens-related: giant papillary conjunctivitis, a reaction to lens deposits, causes itching and mucus in long-term lens wearers.

How contagious is pink eye?

Viral and bacterial conjunctivitis spread by direct contact with eye secretions, for example through hands, towels, pillowcases, makeup or contaminated surfaces, and in the case of some viruses, through respiratory droplets. Viral conjunctivitis can be contagious for as long as the eye is red and watery, often 10 to 14 days. Bacterial conjunctivitis is generally considered much less contagious once appropriate antibiotic treatment has started, typically after about 24 hours.

School and work policies vary between countries. Health services such as the NHS state that children usually do not need to be kept away from school for conjunctivitis unless they feel unwell or there is an outbreak, while other organisations and childcare settings may recommend staying home until discharge settles. Follow local guidance and use common sense, particularly in close-contact settings.

Hygiene: stopping the spread

• Wash your hands frequently with soap and water, especially after touching your eyes, applying drops or wiping discharge.
• Do not share towels, face cloths, pillows, eye drops or makeup.
• Use a fresh cotton pad or tissue for each eye and throw it away immediately.
• Change pillowcases and towels often and wash them at a high temperature.
• Avoid touching or rubbing your eyes.
• Stop wearing contact lenses until the infection has fully cleared and your eye care professional agrees; discard lenses and cases used during the infection. See our contact lens hygiene tips.
• Throw away eye makeup used while infected. See eye makeup safety.
• Avoid swimming pools until the eyes have recovered.

Treatment and self-care

For infective conjunctivitis

1. Gently clean the eyelids and lashes with cotton wool soaked in cooled boiled water, wiping from the inner to outer corner and using a new piece for each wipe.
2. Apply a cool compress for comfort.
3. Use preservative-free lubricating drops to soothe grittiness. See how to choose artificial tears.
4. Take simple pain relief if needed, following the packet instructions.
5. Use antibiotic drops or ointment only if recommended by a pharmacist or doctor. In some countries, certain antibiotic eye drops are available from pharmacies for adults and older children.

Antibiotics do not work against viruses. Steroid eye drops should never be used without examination by an eye specialist, because they can make some infections, especially herpes, much worse and can raise eye pressure.

For allergic conjunctivitis

Avoid known triggers, use cool compresses, rinse the eyes with lubricating drops and use antihistamine or mast cell stabiliser drops recommended by a pharmacist or doctor. Oral antihistamines can help with nose and eye symptoms together but may dry the eyes.

How long recovery takes

Expect bacterial conjunctivitis to improve noticeably within a few days and clear within about a week. Viral conjunctivitis is slower: it often gets worse for three to five days before it starts to settle, and full recovery can take two to three weeks. Allergic conjunctivitis lasts as long as exposure to the trigger continues. If you are not following roughly this course, or if you feel worse instead of better, it is sensible to be re-examined, because the diagnosis may need to be reconsidered.

Conjunctivitis in newborns

Conjunctivitis in the first four weeks of life, called ophthalmia neonatorum, is different from pink eye in older children. It can be caused by bacteria acquired during birth, including gonorrhoea and chlamydia, and can damage the eye quickly or be associated with infection elsewhere in the body, such as pneumonia. Any red eye with discharge in a newborn needs same-day medical assessment.

Not all eye discharge in babies is infection. Many infants have a sticky eye due to a blocked tear duct (nasolacrimal duct obstruction), which causes watering and mucus but a white, comfortable eye. This often improves on its own during the first year with gentle cleaning and massage, but a doctor should confirm the diagnosis. More on infant eye care is in our guide to eye health in children.

Is it really conjunctivitis?

Many conditions cause a red eye, and some threaten sight. Our article on red eye: harmless or an emergency? explains the differences. Conditions that can look like pink eye include:

• Keratitis and corneal ulcers, especially in contact lens wearers (see corneal infections).
• Uveitis, inflammation inside the eye that causes pain and light sensitivity.
• Acute angle-closure glaucoma, which causes severe pain, halos and nausea.
• Dry eye and blepharitis, which cause chronic redness and grittiness.
• Subconjunctival haemorrhage, a painless bright red patch from a burst blood vessel.

When to see a doctor

Speak to a pharmacist, optometrist or doctor if symptoms have not improved after about a week, if they keep coming back, if you wear contact lenses, if you have a weakened immune system or if you are unsure whether it is conjunctivitis.