There are many types of small bumps that can be found on the arms, but the most common are called keratosis pilaris. These are small, red, rough bumps around hair follicles that tend to be on the upper outer arms and are symmetrical on both sides. Products such as lactic acid and glycolic acids can be helpful if applied daily. Unfortunately I cannot tell exactly what you have. Richard Thomas, MD www.SkinCareGuide.ca