Pink eye (conjunctivitis) is an inflammation or infection of the transparent membrane (conjunctiva) that lines your eyelid and covers the white part of your eyeball. When small blood vessels in the conjunctiva become inflamed, they're more visible. This is what causes the whites of your eyes to appear reddish or pink.
Pink eye is commonly caused by a bacterial or viral infection, an allergic reaction, or — in babies — an incompletely opened tear duct.
Though pink eye can be irritating, it rarely affects your vision. Treatments can help ease the discomfort of pink eye. Because pink eye can be contagious, early diagnosis and treatment can help limit its spread.
The most common pink eye symptoms include:
- Redness in one or both eyes
- Itchiness in one or both eyes
- A gritty feeling in one or both eyes
- A discharge in one or both eyes that forms a crust during the night that may prevent your eye or eyes from opening in the morning
When to see a doctor
There are serious eye conditions that can cause eye redness. These conditions may cause eye pain, a feeling that something is stuck in your eye (foreign body sensation), blurred vision and light sensitivity. If you experience these symptoms, seek urgent care.
People who wear contact lenses need to stop wearing their contacts as soon as pink eye symptoms begin. If your symptoms don't start to get better within 12 to 24 hours, make an appointment with your eye doctor to make sure you don't have a more serious eye infection related to contact lens use.
Causes of pink eye include:
- A chemical splash in the eye
- A foreign object in the eye
- In newborns, a blocked tear duct
Viral and bacterial conjunctivitis
Most cases of pink eye are typically caused by adenovirus but can also be caused by herpes simplex virus, varicella-zoster virus, and various other viruses, including the virus that causes coronavirus disease 2019 (COVID-19).
Both viral and bacterial conjunctivitis can occur along with colds or symptoms of a respiratory infection, such as a sore throat. Wearing contact lenses that aren't cleaned properly or aren't your own can cause bacterial conjunctivitis.
Both types are very contagious. They are spread through direct or indirect contact with the liquid that drains from the eye of someone who's infected. One or both eyes may be affected.
Allergic conjunctivitis affects both eyes and is a response to an allergy-causing substance such as pollen. In response to allergens, your body produces an antibody called immunoglobulin E (IgE). This antibody triggers special cells called mast cells in the mucous lining of your eyes and airways to release inflammatory substances, including histamines. Your body's release of histamine can produce a number of allergy signs and symptoms, including red or pink eyes.
If you have allergic conjunctivitis, you may experience intense itching, tearing and inflammation of the eyes — as well as sneezing and watery nasal discharge. Most allergic conjunctivitis can be controlled with allergy eyedrops.
Conjunctivitis resulting from irritation
Irritation from a chemical splash or foreign object in your eye is also associated with conjunctivitis. Sometimes flushing and cleaning the eye to rid it of the chemical or object causes redness and irritation. Signs and symptoms, which may include watery eyes and a mucous discharge, usually clear up on their own within about a day.
If initial flushing doesn't resolve the symptoms, or if the chemical is a caustic one such as lye, you need to be seen by your doctor or eye specialist as soon as possible. A chemical splash into the eye can cause permanent eye damage. Persistent symptoms could also indicate that you still have the foreign body in your eye — or possibly a scratch over the cornea or the covering of the eyeball (sclera).
Risk factors for pink eye include:
- Exposure to something for which you have an allergy (allergic conjunctivitis)
- Exposure to someone infected with the viral or bacterial form of conjunctivitis
- Using contact lenses, especially extended-wear lenses
In both children and adults, pink eye can cause inflammation in the cornea that can affect vision. Prompt evaluation and treatment by your doctor for eye pain, a feeling that something is stuck in your eye (foreign body sensation), blurred vision or light sensitivity can reduce the risk of complications.
Preventing the spread of pink eye
Practice good hygiene to control the spread of pink eye. For instance:
- Don't touch your eyes with your hands.
- Wash your hands often.
- Use a clean towel and washcloth daily.
- Don't share towels or washcloths.
- Change your pillowcases often.
- Throw away your eye cosmetics, such as mascara.
- Don't share eye cosmetics or personal eye care items.
Keep in mind that pink eye is no more contagious than the common cold. It's okay to return to work, school or child care if you're not able to take time off — just stay consistent in practicing good hygiene.
Preventing pink eye in newborns
Newborns' eyes are susceptible to bacteria normally present in the mother's birth canal. These bacteria cause no symptoms in the mother. In rare cases, these bacteria can cause infants to develop a serious form of conjunctivitis known as ophthalmia neonatorum, which needs treatment without delay to preserve sight. That's why shortly after birth, an antibiotic ointment is applied to every newborn's eyes. The ointment helps prevent eye infection.