Can you explain how the body responds to conjunctivitis?

Not in 400 char. :): That is a tough question that would take a full page, but essentially conjunctivitis is inflammation of the clear skin over the white of the eye. It is actually the body's response to either an allergen, infection or other attack on it. Blood vessels engorge and white blood cells enter the area, releasing chemicals to fight the intruder. This leads to the swelling and redness.

Not much: The response is local in the eye lining with the production of antibodies to the infectious agent, production of increased tears to help clean out the eye and swelling of the tissue which helps the antibodies reach their target.