Causes

Español: Causas

Conjunctivitis is a common eye condition worldwide. It causes inflammation (swelling) of the conjunctiva—the thin layer that lines the inside of the eyelid and covers the white part of the eye. Conjunctivitis is often called "pink eye" or "red eye" because it can cause the white of the eye to take on a pink or red color.

The most common causes of conjunctivitis are viruses, bacteria, and allergens. But there are other causes, including chemicals, fungi, certain diseases, and contact lens use (especially the extended-wear type). The conjunctiva can also become irritated by foreign bodies in the eye and by indoor and outdoor air pollution caused, for example, by chemical vapors, fumes, smoke, or dust.

Viral Conjunctivitis

Viral conjunctivitis is caused by infection of the eye with a virus. Viral conjunctivitis

• Can be caused by a number of different viruses, many of which are associated with an upper respiratory tract infection, cold, or sore throat.
• Usually begins in one eye and may progress to the second eye within days.
• Spreads easily and rapidly between people and can result in epidemics.
• Is typically mild, with symptoms being the worst on days 3–5 of infection. The condition usually clears up in 7-14 days without treatment and resolves without any long-term effects. In some cases, it can take 2-3 weeks or more for viral conjunctivitis to completely clear up, depending on whether complications develop.

Bacterial Conjunctivitis

Bacterial conjunctivitis is caused by infection of the eye with certain bacteria. Bacterial conjunctivitis

• Usually begins in one eye and may sometimes progress to the second eye.
• Is a leading cause of children being absent from day care or school (Patel, 2007).
• Cases are typically mild and can last as few as 2-3 days or up to 2-3 weeks. Many cases improve in 2-5 days without treatment (Hurwitz, 2006). However, topical antibiotics are often prescribed to treat the infection.

Allergic Conjunctivitis

Allergic conjunctivitis is caused by the body's reaction to certain substances to which it is allergic, such as pollen from trees, plants, grasses, and weeds; dust mites; molds; dander from animals; contact lenses and lens solution; and cosmetics. Allergic conjunctivitis

• Occurs more frequently among people with other allergic conditions, such as hay fever, asthma, and eczema.
• Usually occurs in both eyes.
• Can occur seasonally, when pollen counts are high.
• Can occur year-round due to indoor allergens, such as dust mites and animal dander.
• May result, in some people, from exposure to certain drugs and cosmetics.
• Clears up once the allergen or irritant is removed or after treatment with allergy medications.