How can i differentiate pink eye from allergic red eyes?

Itching: Both pink eye (a highly contagious infection most often caused by viruses) and allergy eyes can be red, have copious amounts of drainage, and be mattered shut in the mornings. Itching may be the best way to differentiate between the two. Itch is a hallmark for allergic reactions; not much else involves the eyes, ears, nose, and throat like allergies. A doctor can help tell the difference too.

Itchiness : Allergies tend to itch and non allergic don't.