He may just have sensitive skin. DS always has like, tiny little ruptured blood vessels, and what look like bags/bruises under his eyes (only noticeable under certain light) and it's allergies. He also gets bumps on his face,thighs, and the backs of his arms.
His pedi said hydrocortisone cream may help. But I wouldn't know, that was a few years ago and I didn't ever try it because they don't bother him and aren't noticeable.