What is it?
Pink eye (conjunctivitis) is an inflammation or infection of the transparent membrane (conjunctiva) that lines your eyelid and part of your eyeball. Inflammation causes small blood vessels in the conjunctiva to become more prominent, which is what causes the pink or red cast to the whites of your eyes.
The cause of pink eye is commonly a bacterial or viral infection, an allergic reaction or — in babies — an incompletely opened tear duct.
Though the inflammation of pink eye can be irritating, it rarely affects your vision. If you suspect pink eye, you can take steps to ease your discomfort. But because pink eye can be contagious, early diagnosis and treatment is best to help limit its spread.
The most common pink eye symptoms include:
- Redness in one or both eyes
- Itchiness in one or both eyes
- A gritty feeling in one or both eyes
- A discharge in one or both eyes that forms a crust during the night
Causes of pink eye include:
- A chemical splash in the eye
- A foreign object in the eye
- In newborns, a blocked tear duct
Viral and bacterial conjunctivitis
Viral conjunctivitis and bacterial conjunctivitis may affect one or both eyes. Viral conjunctivitis usually produces a watery discharge. Bacterial conjunctivitis often produces a thicker, yellow-green discharge. Both viral and bacterial conjunctivitis can be associated with colds or with symptoms of a respiratory infection, such as a sore throat.
Both viral and bacterial types are very contagious. Adults and children alike can develop both of these types of pink eye. However, bacterial conjunctivitis is more common in children than it is in adults.
Allergic conjunctivitis affects both eyes and is a response to an allergy-causing substance such as pollen. In response to allergens, your body produces an antibody called immunoglobulin E (IgE). This antibody triggers special cells called mast cells in the mucous lining of your eyes and airways to release inflammatory substances, including histamines. Your body's release of histamine can produce a number of allergy signs and symptoms, including red or pink eyes.
If you have allergic conjunctivitis, you may experience intense itching, tearing and inflammation of the eyes — as well as sneezing and watery nasal discharge. Most allergic conjunctivitis can be controlled with allergy eyedrops.
Conjunctivitis resulting from irritation
Irritation from a chemical splash or foreign object in your eye is also associated with conjunctivitis. Sometimes, flushing and cleaning the eye to rid it of the chemical or object causes redness and irritation. Signs and symptoms, which may include watery eyes and a mucous discharge, usually clear up on their own within about a day.
Risk factors for pink eye include:
- Exposure to an allergen for allergic conjunctivitis
- Exposure to someone infected with the viral or bacterial form of conjunctivitis
- Using contact lenses, especially extended-wear lenses
In both children and adults, pink eye can cause inflammation in the cornea that can affect vision. Prompt evaluation and treatment by your doctor can reduce the risk of complications.
To determine whether you have pink eye, your doctor may examine your eyes. Your doctor may also take a sample of eye secretions from your conjunctiva for laboratory analysis to determine which form of infection you have and how best to treat it.