Hair Barrier

Mammalian hair evolved as a partial defense against biting insects like mosquitoes by creating a physical barrier that reduces skin accessibility and alters airflow around the body, making it harder for insects to land and pierce the skin.

Individual hairs increase surface turbulence, which can disrupt mosquito flight and detection of heat and CO₂ plumes, while dense fur in many species physically limits proboscis penetration.

Evolutionarily, this protection is strongest in wild mammals with thick coats, reducing blood loss, parasite transmission, and disease exposure, which provided selective advantages.

In humans, the evolutionary reduction of body hair lessened this defense, but remaining vellus hairs still act as sensory triggers, detecting crawling insects before they bite.