I never had bumps on the back of arms untill a year ago. What are they and how do I get rid of them. Thank you.

Keratosis Pilaris. Check out this website for some info www.mayoclinic.org/diseases-conditions/keratosis-pilaris/.../con-20025750 If this is keratosis Pilaris, it is not harmful, but can be annoying. Using a loofah sponge can help, but don't scrub too hard and hurt the surrounding skin.