Conjunctivitis, or pink eye, is a condition that arises when a delicate structure within the eye becomes inflamed, leading to eye redness, discharge, and other symptoms.
Pink eye can affect children, adults, and even newborns, who may be exposed to bacteria that can cause conjunctivitis during vaginal childbirth.
Some types of conjunctivitis—notably, viral and bacterial—are very contagious. It’s common for the condition to spread from one eye to both eyes within a day or two. Viral and bacterial conjunctivitis may also spread quickly among people within a household or a classroom. Other forms of the condition are not contagious.
A variety of treatments are available for conjunctivitis, although it may resolve on its own without treatment. Most people recover from the condition quickly, with no lasting effects.
What is conjunctivitis?
Conjunctivitis, commonly known as pink eye, causes the whites of the eyes to turn red due to inflammation, infection, and/or irritation. Affected eyes also produce discharge and may burn or itch.
The conjunctiva is a thin membrane that covers the whites of your eyes, as well as the insides of your eyelids. When this structure becomes inflamed, it gives the eyes a reddish appearance and causes other symptoms.
There are several types of conjunctivitis, all of which cause inflammation of the conjunctiva:
- Viral conjunctivitis, which is caused by a virus that can simultaneously cause a cold
- Bacterial conjunctivitis, which is caused by highly contagious bacteria
- Allergic conjunctivitis, which occurs when allergens in the air come into contact with the conjunctiva in the eye, often during certain seasons of the year
- Toxic conjunctivitis, which is the eye’s reaction to a preservative or a drug that causes chronic inflammation of the conjunctiva
Non-specific conjunctivitis, a term used to describe eye redness and discharge when the cause isn’t viral, bacterial, allergic, or toxic. It may be caused by a foreign body in the eye, chronic dry eye, smoke, contact lens overuse, or something else.
What causes conjunctivitis?
Different types of conjunctivitis have different causes.
Viral conjunctivitis is caused by viruses such as:
- Herpes simplex virus
- Epstein–Barr virus
- Newcastle disease
- Zika virus
- SARS-CoV-2, which causes COVID-19
Bacterial conjunctivitis is caused by bacterial infections such as:
- Staphylococcus aureus
- Streptococcus pnemoniae
- Haemophilus influenzae
- Moraxella catarrhalis
- Moraxella lacunata
- Neisseria gonorrhoeae
- Neisseria meningitidis
- Chlamydia trachomatis
- Escherichia coli
Allergic conjunctivitis may be caused by:
- Pet dander
- Dust mites
Toxic conjunctivitis may be caused by:
- Molluscum contagiosum infections
- Phthirus pubis (crab lice) infections of the eyelashes
- Overuse or prolonged use of certain eye medications
Non-specific conjunctivitis may be caused by:
- Dry eye
- A foreign body in the eye
A temporary reaction to an eye wash after exposure to chemicals
What are the symptoms of conjunctivitis?
People who have conjunctivitis may experience:
- Eye redness
- Watery eye discharge
- Mucus discharge from the affected eye (white, yellow, or green)
- Dried crust that “glues” the affected eye shut
- A burning sensation and/or itchiness in the affected eye
- Tears falling from the affected eye
- Swelling of the affected eye
- The feeling that something gritty or sandy is in the affected eye
- Blurry vision
- Sensitivity to bright light
What are the risk factors for conjunctivitis?
People may be at risk of viral or bacterial conjunctivitis if they touch something that a person with conjunctivitis has touched, then touch their own eyes or face.
Sometimes, eye secretions that spread viral or bacterial infection may be present on doorknobs, countertops, the handles of serving utensils, or other high-touch areas. Other times, germs spread more directly from one person’s infected eye to another person’s eye.
Common examples include:
- Sleeping on someone else’s pillow
- Borrowing someone else’s makeup
- Wearing someone else’s glasses
- Using someone else’s towel or handkerchief to wipe your eyes or face
How is conjunctivitis diagnosed?
When your eyes are reddish and producing discharge, doctors may suspect conjunctivitis. To diagnose the condition and determine what type of conjunctivitis you have, you’ll need to share details of your medical history and have a physical examination. In some cases, diagnostic testing may be recommended.
When sharing your medical history, tell your doctor about the symptoms you’ve been experiencing, including when redness and eye discharge began, and if you’ve had a cold, as well as red, burning eyes. It’s also important to mention if you were exposed to an allergen, if other family members recently had pink eye, if you’ve been wearing your contact lenses more than usual, or if you’ve noticed vision changes. Details like these help reveal clues about your condition.
During a physical exam, doctors will examine your eyes, noting the redness of your eye, the color and consistency of any eye discharge, and whether you have eyelid swelling. They’ll also search for foreign bodies in the eye and small bumps on the undersides of your eyelids, which may be a sign of allergic conjunctivitis.
If doctors suspect infectious conjunctivitis, diagnostic lab tests are sometimes recommended to determine whether the condition was caused by a virus or bacteria. If doctors suspect that the conjunctivitis is viral, they may do a rapid test to see if adenovirus—a common cause of viral conjunctivitis—is present so that you don’t take antibiotics unnecessarily. In rare cases, doctors may apply a topical anesthetic to the eye before obtaining a small sample from the conjunctiva for analysis.
How is conjunctivitis treated?
Treatments vary, depending on the type of conjunctivitis you have.
- Viral conjunctivitis. Cool eye compresses may help to soothe crusty eyes, and artificial tears may soothe dry eye. Corticosteroid eye drops may help improve blurry vision or sensitivity to light. Symptoms will gradually improve and fade, as they do for the common cold. All symptoms of viral conjunctivitis should disappear within one to three weeks, although no curative treatments are available.
- Bacterial conjunctivitis. Antibiotics, either in eye drop or ointment form, can help speed up recovery. Newborns are routinely given antibiotic ointment to prevent bacterial conjunctivitis, in case they’re exposed to certain bacteria during childbirth.
- Allergic conjunctivitis. Avoiding the offending allergen should help to eliminate symptoms within a day or less. Taking oral antihistamines before encountering an allergen may prevent or minimize symptoms when a person knows that they will, for example, visit a relative with a cat. To ease discomfort after exposure to an allergen, people may use:
- Antihistamine eye drops, which reduce the effects of the allergen
- Antihistamine-mast cell stabilizer eye drops
- Preservative-free artificial tears, which help to lubricate dry eyes
- Cold compresses, which provide cooling relief
- Topical corticosteroids, for severe cases, which may help to reduce symptoms more quickly
- Tacrolimus ointment, which may be used instead of topical corticosteroids, in some cases
Other types of conjunctivitis may be treated by taking a break from wearing contact lenses or treating dry eye. When conjunctivitis is caused by something in the eye, symptoms should resolve quickly once the eye is cleared of foreign matter.
It’s important to note that contact lens wearers should not wear their contacts if they have any type of conjunctivitis.
What is the outlook for people with conjunctivitis?
Most people recover from conjunctivitis within a short period of time with no lasting damage. In very rare instances, viral or bacterial conjunctivitis may cause scarring of the conjunctiva, which may negatively affect vision.
Washing your hands often and practicing good eye hygiene may help to reduce the spread of viral and bacterial conjunctivitis. Allergic conjunctivitis may be avoided by avoiding exposure to allergens.
This article was medically reviewed by Vicente Diaz, MD.