This condition is called keratosis pilaris and unfortunately is an incurable condition. Because it usually doesn't itch and doesn't have any other side effects other than being ugly, it hasn't gotten much attention in the medical world -- we still don't know exactly what causes it, although some people think it has to do with a problem with desquamation and shedding of skin cells that get clogged in the hair follicles. The only thing you can do is try to treat the cosmetic appearance of it, but treatment must be continual or else any improvement will be lost. Your derm might prescribe a number of hydrating and exfoliating lotions like Am-Lactin, Tazorac, Urea, Carmol, Lac-Hydrin, Retin-A, etc. There are other commercial products like KP Duty sold in Sephora and online. With some people, it gets better with age; with others, it gets worse or stays the same throughout life. Sorry to be the bearer of bad news, but at least it's not life or health threatening!