Looks like you have keratosis pilaris. This is a common, hereditary condition which produces little bumps of keratin protein in the hair follicles in the locations you mention. It has significance beyond appearance. If the bumps bother you, you can exfoliate by rubbing with a loofah or a Buf-Puf sponge, but frankly, the effort isn't usually worth it.
Best.
Dr. Rockoff
Folliculitis (inflamed hair follicles) Google it dude. You got it!
small goose bumps on outer forearms, chins and hands, upper buttocks...Afro American 13 yr old teen...I am grandmother, and been doing lots of research,