"Shaving bumps" is a foreign body inflammatory reaction involving papules and pustules. It primarily affects curly haired men who shave. It can also affect some hirsute black women.
Two mechanisms are involved in the pathogenesis of PFB: (1) extra follicular penetration occurs when a curly hair reenters the skin, and (2) Tran follicular penetration occurs when the sharp tip of a growing hair pierces the follicle wall.
Black men who shave are predisposed to this condition because of their tightly curved hair. The sharp pointed hair from a recent shave briefly surfaces from the skin and reenters a short distance away. The close shave results in a sharp tip below the skin surface, which is then more likely to pierce the follicular wall, causing PFB with Tran follicular penetration.