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Causes
By Mayo Clinic staffCauses of pink eye include:
- Viruses
- Bacteria
- Allergies
- A chemical splash in the eye
- A foreign object in the eye
Viral and bacterial conjunctivitis
Viral conjunctivitis and bacterial conjunctivitis may affect one or both eyes. Viral conjunctivitis usually produces a watery or mucous discharge. Bacterial conjunctivitis often produces a thicker, yellow-green discharge and may be associated with a respiratory infection or with a sore throat. Both viral and bacterial conjunctivitis can be associated with colds.
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
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 itching, sneezing and watery nasal discharge. You may also experience swelling of the membrane (conjunctiva) that lines your eyelids and part of your eyeballs, resulting in what may look like clear blisters on the whites of your eyes.
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 a mucous discharge instead of pus, usually clear up on their own within about a day.
In newborns
In newborns, pink eye may result from an incompletely opened tear duct.
