How do i tell the difference between pink eye and an allergic reaction?

Pink eye: A good question. Pink eye occasionally is caused by alelergy or chemicals but usually spreads from hand to eye as a virus. Less commonly a bacteria. They can look similar but the pink eye often goes away in 7 to 10 days whereas allergic eye problems may persist. There is more discolored eye drainage from a viral pink eye than from an allergic conjuctivitis.