Pink eye can be painful and unsightly. But how contagious is it, really?

Pink eye is among the most unwanted and common infections around. The swollen red eyes, dried pus, and sticky discharge is enough to make anyone suffering with the condition want to avoid being seen in public.

Most of the six million people who experience it each year also want to avoid some of its other more uncomfortable symptoms. These include increased sensitivity to light, an acute burning sensation, or an itchiness that can be so intense for some people that they rub off or loosen some of their eyelashes.

But beyond personal discomfort or public embarrassment, most of us especially don't want to pass the infection onto a loved one or even a stranger. Better understanding of how different forms of pink eye commonly spread can be helpful in this endeavor.

What is pink eye?

Pink eye - also known as conjunctivitis - is an eye infection that happens when the thin outer membrane of the eye, called the conjunctiva, becomes infected and inflamed. "It's the most common ocular condition diagnosed in acute care settings in the United States," says Dr. Daniel Shapiro, a pediatric emergency care physician at UCSF Benioff Children’s Hospital in San Francisco. "And most people will likely develop conjunctivitis at some point in their lives - with the peak incidence occurring during early childhood and early adulthood."

Pink eye can result from a viral infection, a bacterial infection, a chemical (toxin) irritation, or from allergies. "Viral conjunctivitis is worse in the fall and winter," says Dr. John Epling, a practicing family physician and a professor of population health at the Virginia Tech Carilion School of Medicine. This is because it often coincides with the increased presence of respiratory illnesses that are similarly caused by viruses such as when pink eye-adjacent COVID variant Arcturus was spreading rapidly in the fall of 2023. On the other hand, "allergic conjunctivitis can happen in spring, summer and/or fall, depending on the specific allergies a person has," he adds.

Is pink eye contagious?

This timing matters because the type of pink eye one has often determines if one is contagious and how long symptoms will generally last. "Viral conjunctivitis lasts a few days to a week," says Epling, while bacterial pink eye may last until it's treated with drops or ointment, "but should then resolve in a few days." Allergic conjunctivitis "will last as long as allergens like pollens are around, but can be managed with medications and by avoidance of the allergens." For toxic or chemical conjunctivitis, "it's important to seek medical care soon since the treatment can change depending on the exposure," advises Epling.

Of these different types or causes of pink eye, only infectious conjunctivitis (meaning pink eye caused by viruses or bacteria) is contagious, says Shapiro. In both cases, the infection can be spread by direct contact with infected persons or by contact with contaminated objects. "Some viral conjunctivitis is also part of a generalized viral illness such as an infected person also having a fever, cough, nasal congestion, or fatigue," says Shapiro. In such cases, "transmission of the virus through contact or droplets could also lead to development of conjunctivitis as part of a viral syndrome."

Epling warns that virus- and bacteria-caused conjunctivitis "is very contagious," and often "spreads quickly in schools and daycares."

How to prevent pink eye

Because of this, Shapiro says the best way to prevent pink eye caused by bacteria or viruses is to avoid close contact with anyone who currently has the disease (is showing symptoms) and to avoid touching the same surfaces or sharing the same objects such as eyeglasses, makeup, eye drops, towels or bedding.

If your pink eye is caused by seasonal allergies, steering clear of allergens (when possible) or treating it with certain antihistamine or anti-inflammatory eye drops can be helpful, says Epling.

If you have infectious pink eye and want to avoid spreading it to others, it's best to avoid close contact with other individuals while symptoms are present, to avoid touching your eyes, to practice good hygiene by washing hands thoroughly and often, and by not sharing personal items with others or swimming in public pools, per the U.S. Centers for Disease Control and Prevention.

To help alleviate symptoms, Epling advises using a warm compress, getting antibiotic drops or ointment for bacterial conjunctivitis ("antibiotics generally don't help with viral conjunctivitis," he says), gently rinsing eyes with cool or lukewarm water, or using artificial tears to help with dryness and inflammation.

"If symptoms last longer than a few days, it's recommended to see your doctor as complications may have developed," says Epling. "Most primary care doctors can treat conjunctivitis, but occasionally an eye doctor may be needed."

This article originally appeared on USA TODAY: Is pink eye contagious?