The most common types of pink eye spread like respiratory infections, but there are a few other ways to contract conjunctivitis.

By Cindy Kuzma
February 15, 2019

Ask an eye doctor, “How does pink eye spread?” and you might get a single-word response: “Quickly.” But there’s more that goes into understanding what causes pink eye than the knowledge that many cases are highly contagious.

For starters, there are actually three common types of pink eye, medically known as conjunctivitis. (That’s because it’s an infection or irritation of the conjunctiva, the thin tissue that covers the white of your eye and lines your lid.)

Two—viral and bacterial—are the type that can spread from person to person. The third, allergic, involves your surrounding environment.

How can you get pink eye? Knowing the answer to that question is key to avoiding the condition. Here’s more about the underlying causes of pink eye in adults and children.

RELATED: 5 Pink Eye Symptoms to Watch For

The bugs that cause pink eye

Most cases of pink eye are caused by bacteria or viruses, optometrist Shira Kresch, instructor in optometric sciences at Columbia University Medical Center, tells Health.

Viral conjunctivitis is caused by the same types of bugs that cause the common cold, including coronavirus or rhinovirus. Meanwhile, bacterial conjunctivitis and strep throat share some of the same underlying pathogens, says Vivienne Hau, MD, an ophthalmologist with Kaiser Permanente.

How does pink eye start in these cases? An infected person touches his or her eyes, then touches something else. If you touch that person or object and then your eyes, you can contract the same infection. “That includes shaking hands, sharing towels or pillows, or even papers if you work in an office job,” Kresch says.

So when it comes to how to get pink eye, not washing your hands—and frequently touching your face—can both play a big role. “Because conjunctivitis is highly contagious, I can’t emphasize enough how important it is to maintain good hand hygiene,” says Radha Ram, MD, a pediatric ophthalmologist and adult strabismus surgeon with Texas Children’s Specialty Care in Austin.

RELATED: 7 Ways to Get Rid of Pink Eye

Pathogens can also spread when you use old makeup or share makeup. Poor contact lens hygiene is another common way to develop bacterial conjunctivitis, Dr. Hau says.

Always wash and dry your hands before handling your contacts. Use the solution and storage methods recommended by your eye doctor. All these steps become even more important if someone in your household already has pink eye.

If you do develop conjunctivitis yourself, take your contacts out and discard them. Wear glasses until your doctor gives you the OK to put your lenses back in. (And clean your glasses frequently too, since discharge from your eyes may cling to your frames or lenses.) When it’s time to wear contacts again, start with a new pair—as well as a fresh case and a brand-new bottle of solution.

In fact, replace or at least wash everything you can after someone in your household develops bacterial or viral conjunctivitis, including sheets, towels, faucets, and other bathroom fixtures.

Even if you live alone, you can reinfect yourself, “and that’s really the biggest reason why this ends up lasting for weeks in a lot of patients,” says Gene Kim, MD, associate professor of ophthalmology and visual science with McGovern Medical School at UTHealth in Houston and a member of the Robert Cizik Eye Clinic.

RELATED: 8 Home Remedies for Pink Eye

Understanding allergic conjunctivitis

Unlike bacterial and viral conjunctivitis, which are infections, allergic conjunctivitis occurs when your conjunctiva is irritated by something in your surrounding environment. You might develop symptoms during allergy season in the spring or fall, triggered by the same pollen or trees that cause hay fever.

Pet dander is another culprit. “Cats are a very common cause of allergic conjunctivitis, especially if maybe a child hasn’t been around animals much and they slept over at a friend’s who has a cat,” Dr. Hau says. “Their eyes might be all itchy and watery the next day.”

Particles in the air—including smoke from wildfires, cigarettes, or air pollution—also can irritate the eyes. So can chemicals in water, such as chlorine in a swimming pool, as well as creams, cosmetics, and facial cleansers. The best way to avoid allergic conjunctivitis is to steer clear of allergens that irritate your eyes when possible.

RELATED: How to Tell the Differences Between Allergies and Pink Eye

How do you know if you have pink eye?

In most cases, your doctor can tell by the symptoms. These include redness or a pink hue in the whites of your eyes, discharge that may be watery or sticky, swelling of the conjunctiva or eyelid, and a general feeling of discomfort, scratchiness, itching, or burning.

While not every case of pink eye requires medical treatment, Dr. Ram recommends that anyone with a sudden onset of these symptoms see a doctor. Some cases can turn serious, and symptoms can mimic those of other vision-threatening eye conditions.

You might not always know which germ, exactly, is to blame for your infection. While there are sometimes subtle differences in symptoms, your doctor may not perform a culture to see for sure unless your pink eye is serious or doesn’t respond to treatment, Dr. Kim says.

For cases of allergic conjunctivitis, your eye doctor can help you think back through changes in your routine to identify potential culprits. And if you can’t find one, he or she might refer you to an allergist.

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