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
• Tearing

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:

• Viruses
• Bacteria
• Allergies
• 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

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.

In most cases, your doctor can diagnose pink eye by asking questions about your symptoms and recent health history. An office visit is usually not needed.

Rarely, your doctor may take a sample of the liquid that drains from your eye for laboratory analysis (culture). A culture may be needed if your symptoms are severe or if your doctor suspects a high-risk cause, such as a foreign body in your eye, a serious bacterial infection or a sexually transmitted infection.

Pink eye treatment is usually focused on symptom relief. Your doctor may recommend using artificial tears, cleaning your eyelids with a wet cloth, and applying cold or warm compresses several times daily.

If you wear contact lenses, you'll be advised to stop wearing them until treatment is complete. Your doctor will likely recommend that you throw out contacts you've worn if your lenses are disposable.

Disinfect hard lenses overnight before you reuse them. Ask your doctor if you should discard and replace your contact lens accessories, such as the lens case used before or during the illness. Also replace any eye makeup used before your illness.

In most cases, you won't need antibiotic eyedrops. Since conjunctivitis is usually viral, antibiotics won't help, and may even cause harm by reducing their effectiveness in the future or causing a medication reaction. Instead, the virus needs time to run its course — up to two or three weeks.

Viral conjunctivitis often begins in one eye and then infects the other eye within a few days. Your signs and symptoms should gradually clear on their own.

Antiviral medications may be an option if your doctor determines that your viral conjunctivitis is caused by the herpes simplex virus.

Treatment for allergic conjunctivitis

If the irritation is allergic conjunctivitis, your doctor may prescribe one of many different types of eyedrops for people with allergies. These may include medications that help control allergic reactions, such as antihistamines and mast cell stabilizers, or drugs that help control inflammation, such as decongestants, steroids and anti-inflammatory drops.

Over-the-counter eyedrops that contain antihistamines and anti-inflammatory medications also may be effective. Ask your doctor if you're not sure which product to use.

You may also reduce the severity of your allergic conjunctivitis symptoms by avoiding whatever causes your allergies when possible.

To help you cope with the signs and symptoms of pink eye until it goes away, try to:

• Apply a compress to your eyes. To make a compress, soak a clean, lint-free cloth in water and wring it out before applying it gently to your closed eyelids. Generally, a cool water compress will feel the most soothing, but you can also use a warm compress if that feels better to you. If pink eye affects only one eye, don't touch both eyes with the same cloth. This reduces the risk of spreading pink eye from one eye to the other.
• Try eyedrops. Over-the-counter eyedrops called artificial tears may relieve symptoms. Some eyedrops contain antihistamines or other medications that can be helpful for people with allergic conjunctivitis.
• Stop wearing contact lenses. If you wear contact lenses, you may need to stop wearing them until your eyes feel better. How long you'll need to go without contact lenses depends on what's causing your conjunctivitis. Ask your doctor whether you should throw away your disposable contacts, as well as your cleaning solution and lens case. If your lenses aren't disposable, clean them thoroughly before reusing them.

Start by seeing your family doctor or a general practitioner if you have any eye-related signs or symptoms that worry you. If your signs and symptoms persist or get worse, despite treatment, your doctor may refer you to an eye specialist (ophthalmologist).

Because appointments can be brief, and because there's often a lot of ground to cover, it's a good idea to be well prepared for your appointment. Here's some information to help you get ready for your appointment and what to expect from your doctor.

What you can do

• Be aware of any pre-appointment restrictions. At the time you make the appointment, be sure to ask if there's anything you need to do in advance, such as stop wearing contact lenses or refrain from using eyedrops.
• Write down any symptoms you're experiencing, including any that may seem unrelated to the reason for which you scheduled the appointment.
• Make a list of all medications, vitamins or supplements that you're taking.
• Write down questions to ask your doctor.

Your time with your doctor is limited, so preparing a list of questions can help you make the most of your time together. List your questions from most important to least important in case time runs out. For pink eye, some basic questions to ask your doctor include:

• What's the most likely cause of my symptoms?
• What kinds of tests do I need?
• What treatments are available?
• How long will I be contagious after starting treatment?
• Is there a generic alternative to the medicine you're prescribing me?
• Are there any brochures or other printed material that I can take with me? What websites do you recommend?
• Do I need to come back for a follow-up visit?

In addition to the questions that you've prepared to ask your doctor, don't hesitate to ask additional questions.

What to expect from your doctor

Your doctor is likely to ask you a number of questions. Being ready to answer them may allow time later to cover points you want to address. Your doctor may ask:

• When did you begin experiencing symptoms?
• Have your symptoms been continuous or occasional?
• How severe are your symptoms?
• Does anything improve your symptoms?
• What, if anything, appears to worsen your symptoms?
• Do your symptoms affect one eye or both eyes?
• Do you use contact lenses?
• How do you clean your contact lenses?
• How often do you replace your contact lens storage case?
• Have you had close contact with anyone who has pink eye or cold or flu symptoms?

What you can do in the meantime

Stop using contact lenses until you can see your doctor. Wash your hands frequently to lessen the chance of infecting other people. Don't share towels with other people for the same reason.