For how long should I be avoiding sun exposure after dermabrasion? I am aware that dermabrasion may cause some skin irritation. For how long avoiding sun exposure is necessary following the skin smoothing procedure for removal of small dry bumps on my arm

It . It sounds like you are talking about keratosis pilaris. The sun doesn't really play a role in this condition (proper use of sunscreen after microdermabrasion is always a good idea, though). This is, unfortunately, a chronic condition for many people. It does tend to settle a bit with age in many patients. Treatment options include keratolytic agents such as Lactic Acid creams, salicylic acid creams, urea based creams, retinoids (like retin-a), and microdermabrasion. Because microdermabrasion is a bit more expensive, most patients opt for the topical creams. I hope that helps.