Is it true that blue eyed people are allergic to the sun?

No: Fair-skinned people may have increased skin sensitivity to sunlight developing an itchy rash on upper back, neck, "v" of the chest, upper arms & forearms called polymorphous light eruption aka sun poisoning. Some people sneeze when they walk out into bright sunlight. This is a nervous system reflex & not an allergic reaction. It's called solar sneezing. Eye color is unrelated to either condition.

No: Blue-eyed people are not prone to develop solar urticaria or sun-induced hives.