This is some information I found through the web:
Conjunctivitis, commonly known as pink eye, is an infection of the conjunctiva (the outer-most layer of the eye that covers the sclera).

The three most common types of conjunctivitis are: viral, allergic, and bacterial. The viral type is often associated with an upper respiratory tract infection, cold, or sore throat. The signs and symptoms of viral conjunctivitis are : watery discharge, irritation, red eye. Infection usually begins with one eye, but may spread easily to the fellow eye.

The allergic type occurs more frequently among those with allergic conditions. The signs and symptoms of allergic conjunctivitis are: usually affects both eyes, itching, tearing, swollen eyelids.

Bacterial conjunctivitis is often caused by bacteria such as staphylococcus and streptococcus. The signs and symptoms of bacterial conjunctivitis are: stringy moderate to large amount of discharge (pus) which are caused by bacteria , usually yellow or greenish in color that may cause the lids to stick together, especially after sleeping; swelling of the conjunctiva, redness, tearing, irritation and/or a gritty feeling, usually affects only one eye, but may spread easily to the fellow eye.

Conjunctivitis is diagnosed during a routine eye exam using a slit lamp microscope. In some cases, cultures are taken to determine the type of bacteria causing the infection.

Conjunctivitis requires medical attention. The appropriate treatment depends on the cause of the problem. To avoid spreading infection, take these simple steps: disinfect surfaces such as doorknobs and counters with diluted bleach solution, donot swim (some bacteria can be spread in the water), avoid touching the face, wash hands frequently.