What Causes Itchy Red Bumps All Over The Body?

for about the last week i have itchy red bumbs appear all over my body. mainly on my legs. They itch worse at night and they end up bleeding because of it. they look like bites of some kind not a rash. I have not changed any detergents or soaps or anything in that nature. I have spots behind my ears as well. None of the spots are close together, they are just kind of scattered.