Kathi Valeii is a freelance writer covering the intersections of health, parenting, and social justice.

Christine L. Larsen, MD, is a board-certified ophthalmologist who serves as adjunct clinical faculty, specializing in glaucoma and cataract surgery, at the University of Minnesota.

Pink eye (conjunctivitis ) is when the conjunctiva (the membrane covering the eyeball) becomes inflamed or infected. Your eyes will likely be red, itchy, watery, and crusty if you have pink eye.

Pink eye is primarily caused by viruses, bacteria, allergens, or other irritants. The infection usually lasts one to three weeks, depending on the cause.

This article explains pink eye types, diagnosis, and treatment.

Pink eye occurs when something irritates the eye. Causes include a virus, bacteria, allergen, or some other irritant.

A virus causes viral pink eye. The adenovirus (responsible for the common cold) typically causes pink eye. It spreads the way many other viruses spread through exposure to someone else's cough or sneeze.

Viral pink eye can also spread within your body. For example, if you have a cold or other upper respiratory infection, the infection can move through your connected mucous membranes (from your nose to your tear ducts).

Symptoms of viral pink eye include:

Most cases of viral pink eye are mild and clear up within one to two weeks. However, it can sometimes linger for as long as three weeks.

A bacterial infection causes bacterial pink eye. Staphylococcal or streptococcal bacteria are often responsible for pink eye. This bacteria enters your eye through physical contact, rubbing your eye, or using contaminated makeup or other beauty products.

Symptoms of bacterial pink eye include:

Bacterial pink eye can be mild and go away on its own in a few days. However, it can take up to two weeks to completely clear and may require antibiotics.

Pink eye generally lasts between one to three weeks. Both viral and bacterial infections can be mild and go away independently. However, bacterial infections may require antibiotics to clear fully. In addition, allergies and chemical irritants can cause pink eye. Usually, removing the allergen or irritant resolves the problem.

A healthcare provider can diagnose pink eye through a physical exam and evaluate your medical history and symptoms.

Sometimes they will also collect a sample of your eye discharge to have a lab evaluate what type of pathogen is causing your infection to determine the best treatment. A culture isn't always necessary, though, since certain clinical signs indicate an infection is viral, bacterial, or allergenic.

Often, pink eye will resolve in a couple of weeks. However, other times it requires treatment. Overall, pink eye treatment aims to reduce discomfort, resolve the infection, and prevent it from spreading.

How you resolve the infection depends on what is causing your pink eye.

Pink eye is very contagious. Therefore, the best way to prevent infection is through good hygiene practices, like hand washing and avoiding touching your eyes. To prevent pink eye, consider the following:

Often, pink eye resolves on its own within a couple of weeks. Still, it's good to make an appointment with an ophthalmologist, optometrist, or healthcare provider. They will be able to diagnose what is causing your infection and provide a treatment plan to offer relief.

Viruses, bacteria, allergens, and irritants cause pink eye. This infection leads to inflammation, redness, itching, and eye discharge. Usually, pink eye resolves on its own in one to three weeks. However, bacterial infections may require antibiotic eye drops. In addition, comfort measures like cool compresses and artificial tears may provide relief.

If you have allergies or an upper respiratory infection, it can sometimes be hard to tell if itchy, irritated eyes are a side effect of your ailment or due to pink eye. In this case, discharge or crusting may tell you something else is happening. Since pink eye is highly contagious, keep it from spreading by frequently washing your hands, avoiding touching your eyes, and not sharing towels with family members while you are sick.

The best way to encourage pink eye to heal is to take care of yourself and use good hygiene practices. You may require antibiotic eye drops in some cases of bacterial pink eye. Clean the discharge around your eye with a cotton ball and apply cool compresses to combat pain and swelling.

Pink eye is highly contagious and spreads quickly. If you have pink eye, you are contagious for as long as you have symptoms. If you have bacterial pink eye and are using an antibiotic, you are contagious until you have been using antibiotics for 24 hours. Pink eye caused by allergens and irritants is not contagious.

Pink eye often goes away on its own, usually in one to three weeks. However, sometimes bacterial pink eye requires antibiotic eye drops. You can also use at-home measures like a warm compress and artificial tears to alleviate discomfort while you heal.

Centers for Disease Control and Prevention. Conjunctivitis (pink eye): symptoms.

American Optometric Association. Conjunctivitis (pink eye).

American Academy of Ophthalmology. Conjunctivitis: what is pink eye?

Centers for Disease Control and Prevention. Conjunctivitis (pink eye): diagnosis.

Centers for Disease Control and Prevention. Conjunctivitis (pink eye): prevention.

Nemours Teen Health. Pink eye (conjunctivitis).

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