Pink eye, also known as conjunctivitis, develops when the blood vessels in the transparent membrane, or conjunctiva, that line the eyelid and the white part of the eyeball get inflamed. The inflamed membranes’ veins swell and gives the whites of the eyes a distinct pink or red tint, which is where it gets its name.
Pink eye is one of the most common ailments to affect both children and adults, according to the Centers for Disease Control and Prevention (CDC), and conjunctivitis is a leading cause of children being absent from day care or school.
Contrary to popular belief, though, pink eye isn’t always contagious. There are four different factors that can cause pink eye: an allergic reaction, a foreign substance in the eye, a viral infection or a bacterial infection.
Viral conjunctivitis is the most common form of pink eye; it is caused by a cold virus, according to the American Academy of Ophthalmology. It can also be caused by the herpes simplex virus. Bacterial conjunctivitis is caused by a bacterial infection of the eye.
Allergic conjunctivitis is simply caused by allergens irritating the conjunctiva membrane. Any object in the eye, including contacts, dirt and liquids can also cause conjunctivitis. Allergic conjunctivitis and conjunctivitis caused by a foreign substance in the eye aren’t contagious.
On the other hand, when it is caused by a bacterial or viral infection, pink eye can be very contagious. “It is spread when a person touches his or her own eye and then touches the eye of another person; or it is spread to the individual by touching the infection in one’s own nose or sinus,”said Dr. Jill Swartz, practicing physician at GoHealth Urgent Care.