Red eye in adults: pink eye, allergy, dry eye or something serious? Is it contagious and can I go to work?

Most red eyes in adults are viral, allergic or dry, and they settle within one to two weeks. A red eye with pain, blurred vision, sensitivity to light, or a red eye in someone who wears contact lenses is different, and needs an eye review the same day. Whether it is contagious and whether you can go to work depends on which kind it is, and the official advice is not the same everywhere.

If the red eye belongs to a child, Little Eyes 101 has a separate page on pink eye in children, written for parents. This article is about adults.

What are the common causes of a red eye in adults?

The common ones are conjunctivitis (pink eye), dry eye, a burst blood vessel, an inflamed eyelid margin, an ingrowing eyelash and other eyelid problems. The NHS red eye page names exactly this list. Contact lens wear and allergy sit across several of them.

Conjunctivitis is inflammation of the conjunctiva, the thin clear membrane over the white of the eye and the inside of the lids. When it is inflamed, the small vessels in it widen and the white looks pink or red. The same widening happens when the surface is dry, or when the lid margin next to it is inflamed. So redness is a sign, not a diagnosis, and the useful question is what is driving it.

The word "pink eye" tends to cover everything. In practice a doctor wants to know three things: is there pain or a change in vision, is there discharge, and does it itch. Those three answers separate most of the causes that follow.

How can I tell viral, bacterial and allergic pink eye apart?

By the discharge and the itch. The American Academy of Ophthalmology describes viral conjunctivitis as burning, red eyes with a watery discharge, bacterial as sore, red eyes with a lot of sticky pus, and allergic as intense itching, puffiness and watering.

The 2013 JAMA systematic review of conjunctivitis adds a useful sorting rule. Viral conjunctivitis is the most common infectious cause, and usually needs no treatment. Bacterial conjunctivitis is the second most common, and most uncomplicated cases resolve in one to two weeks. The factors most strongly linked to bacterial conjunctivitis were lids stuck together on waking, absence of itching, and no history of conjunctivitis. Allergic conjunctivitis is encountered in up to 40 per cent of the population, and itching is its most consistent sign.

These are patterns, not proof. A viral eye can be sticky in the morning, and an allergic eye can be infected on top. If you are unsure, an examination decides it, and it should decide it sooner if you wear lenses.

Is a red eye contagious?

Viral and bacterial conjunctivitis are. Allergic conjunctivitis is not, and neither are dry eye, a burst vessel or most lid problems. The CDC says viral and bacterial pink eye are very contagious, and the NHS says allergic conjunctivitis is not contagious.

The spread is by hands, towels, pillows and shared eye products. The CDC advises washing the hands often with soap and water for at least 20 seconds, washing pillowcases, sheets, washcloths and towels often in hot water and detergent, and not sharing pillows, washcloths, towels, eye drops, eye or face make-up or make-up brushes. The NHS adds: do not rub your eyes.

The sharing of make-up matters more than people think. A mascara wand or eyeliner pencil that touched an infected eye carries the infection to the next eye. If you have had a red, sticky eye, I would bin the eye make-up you used during it, which is my own precaution, not a rule from the sources above.

Can I go to work with pink eye?

It depends on the source, and they genuinely disagree. The NHS says you do not need to stay away from work or school unless you feel very unwell. The American Academy of Ophthalmology says that with bacterial or viral conjunctivitis you should stay home and avoid contact with other people, and not return to the gym, school or work until the eyes are no longer red with discharge. The CDC sits between them: with no fever or other symptoms you may return with your doctor's approval, but you should stay away while symptoms last if your work involves close contact with others.

The honest summary is that nobody has a number of days that fits everyone. The marker the stricter sources use is practical: redness with discharge. My view is that the work matters more than the rule. A desk job with your own keyboard and good hand-washing carries little risk to others. A job with close contact, shared equipment or food is a different matter, and an employer's policy then decides in practice. Ask for it, and bring a note from your doctor that says which type you have.

If it is allergic, there is nothing to pass on, and no reason to stay away. For children in a taska or tadika, Little Eyes 101 sets out the Malaysian guideline and the three official answers in its page on sakit mata and how long a child must stay home.

How long does a red eye last, and what helps?

Conjunctivitis usually clears in one to two weeks. The CDC says viral pink eye usually clears in 7 to 14 days without treatment but can take two to three weeks or longer, and bacterial pink eye often clears in 2 to 5 days without treatment, with full clearing taking about two weeks.

Treatment follows the type. Antibiotics work only for bacterial infection, not for viral or allergic conjunctivitis, which is why asking for them for every red eye is a poor idea. The CDC lists cold compresses and artificial tears for comfort, antiviral medicine only for severe cases caused by herpes viruses, and antihistamine drops and removing the trigger for allergy. The NHS advises seeing a GP if symptoms have not cleared in seven days.

Wash the lids with cooled boiled water and a clean cotton pad for each eye, which is the NHS advice, and stop wearing contact lenses until the eye has recovered. For the pharmacy shelf, including why whitening and steroid drops are a poor choice, see my guide to pharmacy eye drops for a red eye.

Which red eyes are not pink eye, and need a doctor today?

The ones with pain, light sensitivity, changed vision, injury or contact lens wear. The NHS says to go to A&E for a red eye with any change in sight such as wavy lines, flashing or loss of vision, pain on looking at light, a severe headache with feeling sick, a very dark red eye, an injury or chemical splash, or one pupil bigger than the other. It advises an urgent appointment if the eye is very painful and red, or if you wear contact lenses, because you could have an infection.

The American Academy of Ophthalmology gives the same message in its own words: contact an ophthalmologist immediately for moderate to severe pain, blurred vision, increased sensitivity to light or intense redness, or if symptoms get worse instead of improving. In a lens wearer, the worry is an infection of the cornea, the clear window at the front of the eye. Take the lenses out, do not put them back in, and have the eye seen. I cover how lens habits raise that risk in my article on contact lens myths.

Some red eyes are harmless and look dramatic. A flat, bright red patch with no pain is often a burst vessel, which I explain in my guide to subconjunctival haemorrhage. And in haze, itching and swelling together may be allergic, as I discuss in the page on haze and your eyelids.

When is the red eye really an eyelid problem?

When it keeps coming back, or stays red and sticky in one eye despite drops. The lid margin, the edge that carries the lashes, is a common hidden cause. Blepharitis, an ingrowing lash and a blocked tear duct system can all make the eye look like permanent pink eye.

The NHS names both blepharitis and an ingrowing eyelash among the causes of a red eye. A red, sticky eye that does not clear with antibiotic drops may be canaliculitis, an infection in the tiny drainage canal of the lid, which I describe in my article on canaliculitis. Crusted, sore lids are covered in the page on blepharitis.

For the wider picture of the front of the eye, see the eye surface section, and for why eyes look tired and red together, my hub article.