It is so common that many dermatologists consider it a skin type instead of a medical condition. It usually starts in childhood but becomes more obvious during the teenage years and adulthood. About 50% to 80% of teenagers and 40% of adults will develop these bumps at some point during their lives. It is the most common disorder of the hair follicle in children, and estimates of its prevalence in adults range from 0.75% to 34% of the population.