Pilaris

Keratosis pilaris (KP) is a very common genetic follicular condition that is manifested by the appearance of rough bumps on the skin and hence colloquially referred to as "chicken skin". It most often appears on the back and outer sides of the upper arms (though the lower arms can also be affected), and can also occur on the thighs and tops of legs, flanks, buttocks or any body part except glabrous skin (like the palms or soles of feet). Less commonly, lesions appear on the face and may be mistaken for acne.

See complete Wikipedia article here.

For more information from the American Academy of Dermatology click here.