Acute conjunctivitis caused by bacterial or viral infections is commonly known as pink eye, which is highly contagious.

Most cases of pink eye are spread through the hand - eye - hand route. That is, if a person touches their eyes and then touches other objects, and someone else touches those objects and then their own eyes, the infection can spread.

Other types of conjunctivitis are not pink eye.

Some cases of chronic conjunctivitis are also caused by bacterial or viral infections. However, since the virulence of the bacteria or viruses is relatively weak, the course of the disease is milder, progresses more slowly, and it is not contagious.

Allergic conjunctivitis occurs when the eyes come into contact with allergens, and the main symptom is itchy eyes.