Conjunctivitis, commonly known as “pink eye”, refers to the inflammation of the conjunctiva of the eye. The conjunctiva is a thin, clear mucus membrane that covers the whites of the eye and lines the inside of the eyelids. It is involved in the production of mucus and tears to provide lubrication, and also functions as a protective barrier to the eye.

Three Main Types of Conjunctivitis:

Allergic conjunctivitis is often seen in people suffering from atopic conditions, such as hay fever, asthma, and eczema. It is not contagious and may be caused by a number of allergens, including pollen and animal dander. Another subtype of allergic conjunctivitis, giant papillary conjunctivitis, may be seen in those wearing hard lenses, some contact lens wearers, with chronic eye allergies, or having an artificial eye. Allergic conjunctivitis typically manifests with clear, watery discharge, mild conjunctival injection, and itching in both eyes. It may be accompanied by other symptoms such as nasal discharge and sneezing.

Infectious conjunctivitis arises from an infection of the conjunctiva by a bacteria or virus. Both subtypes are extremely contagious. Viral conjunctivitis is the most common type of conjunctivitis, usually caused by adenovirus, but may be the result of other viruses such as the herpes simplex virus as well. Viral conjunctivitis may occur in one or both eyes, and is characterized by sudden onset of red, itchy, watery eyes that may have a foreign body sensation or be sensitive to light. It is often preceded by a respiratory infection or exposure to a sick contact. Bacterial conjunctivitis is more common in children and is usually caused by Haemophilus influenza, Streptococcus pneumonia, and Moraxella catarrhalis. Bacterial conjunctivitis may occur in one or both eyes and presents with conjunctival injection, mucopurulent or purulent discharge, sticking of the eyelids, or presence of crusting, but lacks symptoms seen in other types of conjunctivitis, such as watery discharge and itching.

Chemical conjunctivitis may result from exposure to air pollution, chlorine in swimming pools, or other environmental irritants. Symptoms and severity of chemical conjunctivitis vary depending on what the noxious substance is but can include watery discharge, crusting on eyelids, eye pain, foreign body sensation, and sensitivity to light.

Source: American Optometric Association. (n.d.). Conjunctivitis (pink eye). AOA. Retrieved April 30, 2022, from