What are these itchy non discolored bumps?

My little brother has some itchy bumps across his stomach that run up to his armpit on one side. They are skin colored not red, and are flat topped. They vary in size from about twice the size of a pin head to a little bigger than a nickel. By flat topped I mean they are not rounded, I guess they are sort of like mesas- raised from skin level but with a surface parallel to it. I have seen them before but I cannot remember where or what they were from.