Tiny, stubborn bumps on the backs of your upper arms are likely caused by keratosis pilaris, a condition in which keratin (a protein in the skin) forms hard plugs within hair follicles. Daily use of an over-the-counter glycolic or lactic acid lotion should clear it up in a few weeks; avoid scrubs, which can cause further inflammation. A 1 percent hydrocortisone cream may reduce any accompanying redness.
To eliminate discoloration on the arms, many doctors use photodynamic therapy (PDT), which treats both the aesthetic issue and the precancerous lesions that can appear in this area. The arms are painted with a photosensitizing chemical that's activated with light, leaving the skin red, swollen, and a little sore for up to four days. After a week, it's brighter and much more even-toned; one or two sessions usually suffice. To address both discoloration and crepiness, a fractionated nonablative laser is a popular choice; three to five treatments do the trick.