My 13 Yr Old Brother Has Several Small, Slightly Raised

My 13 yr old brother has several small, slightly raised itchy red bumps all over his body. They are extremely itchy and seem to be non contagious. He has no fever or illness so it seems this must be some sort of rash. The itchy bumps cover his back, stomach, legs, arms although not behind the knees or under the armpits. We have already tried Eczema medication and this did not work. After itching, the numerous small bumps did not ooze pus, only a small amount of blood rose to the surface which later scabs and becomes a whitish brown scar. After they heal they don't itch and the rash seems to be mainly concentrated on his back, stomach, upper thigh, and shoulders. He has really bad allergies so could this be an allergen issue? Thank you so much for your help!