Ingrown hairs occur when hair is cut and the hair grows back in at an improper angle penetrating the skin rather than exiting the skin's surface.
An ingrown hair, or Pseudofolliculitis barbae, is when the sharp tip of a hair curls in and grows sideways into the skin rather than growing outwards. The condition is more common in areas where coarse hair tends to grow such as pubic hair and in facial hair in men.
The body recognises the ingrown hair as a foreign body so reacts with an inflammatory response that includes itchiness, redness and a raised spot that sometimes becomes infected and fills with pus. Most ingrown hairs are caused by hair that is removed through hair removal techniques such as shaving, waxing, tweezing or electrolysis.
These procedures have the potential to irritate the hair follicle which can result in inflammation. While mostly ingrown hairs are harmless, they can lead to scarring, skin discolouration and skin infection.