Hair grows inside the tubes in the skin called follicles. When shaved, the tip of the hair is left creating a sharp point. When this curly hair grows, the sharp tip occasionally will curve back and pierce the skin, thus irritating it and creating a razor bump. The medical term for the process of PFB is “Transfollicular Penetration.”
The body treats all ingrown hairs just as it would a splinter or any object that may seem foreign to it by producing an inflammatory pimple-like bump. Razor bumps can affect any individual who has curly hair whose hair follicles are orientated at oblique angles to the surface of the skin, making it easier for the shaved, sharp-tipped hairs to re-enter the skin.