From Paule Begoun:
[SIZE=12pt]Keratosis Pilaris[/SIZE]
What Causes This Problem: Clogged pores are the cause of keratosis pilaris—a skin condition where little, raised red bumps show up in patches on your upper arms, backside, or thighs. The bumps resemble chicken skin and can appear as small, red, inflamed pimples that occasionally itch, but most often they are just benign bumps that are visible on the skin and feel rough.
The Solution: Although there is no cure for these bumpy rough spots, it is possible to control the problem by unclogging the pores with gentle exfoliation, but NOT by scrubbing.
The right exfoliant can make a HUGE difference; in many cases, keratosis pilaris can be kept completely under control, meaning that there will be no visible signs of the condition as long as you continue to use the exfoliant.
Without question, the best way to reduce or get rid of these bumps is to use a product that contains beta hydroxy acid (BHA, also known as salicylic acid) listed as an active ingredient and that has a pH low enough for exfoliation to occur.
Two other interesting aspects of BHA are (1) it has antimicrobial properties, so it helps control the bacteria that may be causing the pimple-like eruptions, and (2) because it has anti-inflammatory properties it helps reduce or eliminate redness and inflammation.