Question: what causes bumps on back of upper arms?
Answer: Keratosis pilaris. Keratosis pilaris causes small bumps to appear on the upper arms, legs or buttocks. They usually don't hurt or itch. Keratosis pilaris (ker-uh-TOE-sis pih-LAIR-is) is a common, harmless skin condition that causes dry, rough patches and tiny bumps, usually on the upper arms, thighs, cheeks or buttocks ...