Are you sure the tiny hard pustules aren't just keratosis pilaris[0]? I've always had tiny, hard red bumps on my arms and thighs. It's genetic and harmless. The body just overproduces keratin in the skin and it gets trapped in the hair follicles, plugging them up. Keratin is hard - it's the same protein that makes hair and fingernails.

[0] http://en.wikipedia.org/wiki/Keratosis_pilaris