Reflections

Ingrown hairs (Pseudofolliculitis barbae) appear on skin when hair is cut, and the hair grows back in at an improper angle.

The process of cutting the end of the hair shaft through shaving can force hair back into its follicle, or even cause hair to double over on itself, re-entering the same follicle and growing inward instead of exiting the surface. The hair shaft can also grow and enter another follicle.

The body recognizes this ingrown hair as a foreign body (similar to the way it would a splinter), and triggers an inflammatory response that includes redness, pain, and a raised area that resembles a pimple that can fill with pus.