Humans have armpit hair for multiple important biological and evolutionary reasons. Armpit hair helps provide natural insulation by trapping body heat, which is useful in regulating body temperature. It also acts like an absorbent to hold sweat, aiding in cooling the skin during warm weather. Additionally, armpit hair helps control odor by trapping odor-causing bacteria, limiting their interaction with the skin that produces foul smell. Beyond thermoregulation and odor control, armpit hair plays a role in sexual signaling by helping distribute pheromones, chemical compounds linked to sexual attraction. The hair holds and disperses these pheromones through arm movement, which historically helped signal fitness for mating. Armpit hair also reduces friction between the skin of the arm and torso during activities like running or walking, thus protecting the skin. Culturally, perceptions and grooming practices regarding armpit hair vary widely around the world, with some cultures favoring removal and others embracing natural body hair. In sum, armpit hair serves functional roles in temperature regulation, odor control, sexual signaling, and skin protection rooted in human evolution and biology.
