How do doctors identify conjunctivitis?

Eye exam: Conjunctivitis is either allergic or infectious and is diagnosed by a combination of symptoms of itching, burning, redness, weeping along with physical findings of dilated blood vessels, mucous membrane inflammatory patterns, and discharge pattern. Sometimes there is swollen lymph node in front of the ear.

H & P: The best way to diagnose & treat conjunctivitis is by a carefully taken history & physical examination of the eye and periocular adnexa. This is the methodology that makes a clinician a clinician.