Pink eye (conjunctivitis) causes
Pink eye, more accurately called conjunctivitis, does not have a single, universal cause. Technically, conjunctivitis is only pink eye when it’s caused by a virus. But conjunctivitis can also be caused by bacteria or allergies.
There are several types of pink eye, each with its own cause.
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Viral pink eye causes
Viral conjunctivitis is caused by one of many common viruses, including those responsible for the common cold. It sometimes occurs alongside a cold, flu or other upper respiratory infection.
This form of pink eye is very contagious. It can be transferred when you share personal items, touch your eyes before washing your hands, and being close to other sick people, especially if they’re coughing or sneezing.
These are some of the activities that can lead children to contract viral pink eye more often than adults. Certain methods of prevention can reduce the chances of getting pink eye.
Less commonly, pink eye may be caused by the coronavirus responsible for COVID-19. This can occur with or without other COVID-related symptoms.
If you think you may have COVID-19, the CDC recommends quarantining for at least 14 days, closely monitoring your symptoms and staying away from others as much as possible.
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Bacterial conjunctivitis causes
One of several different bacteria can be responsible for bacterial conjunctivitis.
Like viral pink eye, the bacterial version is also spread via physical contact, for example touching your eyes with unclean hands. This type of conjunctivitis answers questions like, “is pink eye caused by poop?” and emphasizes the need for thorough, regular hand washing, especially before touching the eyes.
Rarely, this type of conjunctivitis can cause serious damage to the eye if left untreated. Scheduling an appointment with an eye doctor will ensure proper treatment and a quick recovery.
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Sexually transmitted diseases (STDs), namely gonorrhea, can also cause bacterial conjunctivitis. This usually occurs when an unwashed hand or bodily fluid transfers the bacteria onto the eye’s surface. Pink eye is most commonly seen in newborns whose mothers have active infection.
Allergic conjunctivitis causes
Allergens in the environment can cause a type of “pink eye” called allergic conjunctivitis.
Eye irritants like pollen, dust and animal dander are common culprits among people who are susceptible to allergies. Itchy, red eyes may be seasonal (e.g., pollen) or flare up year-round (e.g., dust and pet dander).
Certain medications or chemicals, like the ones found in cigarette smoke or swimming pools, can also lead to allergic conjunctivitis.
The whites of our eyes are covered with a thin, clear membrane called the conjunctiva. When tiny allergen particles come into contact with the conjunctiva, it gets itchy, watery or bloodshot.
Treating the body’s response to the allergen, or changing your environment, usually reduces or eliminates the eye-related symptoms.
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Giant papillary conjunctivitis (GPC) is a secondary form of allergic conjunctivitis, characterized by tearing, watering and a “bumpy” underside of the upper eyelid(s).
GPC is usually caused by an allergic reaction to contact lenses, but it can also show up in people with an artificial eye (ocular prosthesis), patients with eye stitches or sutures, among others.
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When to see an eye doctor
Any time you experience new or sudden eye redness or irritation for an extended period of time, you should schedule an appointment with an eye doctor.
While serious conditions or complications are rare, they can happen. An eye care professional will be able to diagnose your condition, rule out other eye infections and prescribe any remedies necessary.
Page published in August 2020
Page updated in November 2021