Microscopic eight-legged mites live in your hair follicles and crawl across your face at night while you sleep.

Demodex mites are microscopic arachnids that have co-evolved with humans for thousands of years. Two species—Demodex folliculorum and Demodex brevis—are found exclusively on human skin. D. folliculorum typically inhabits hair follicles, while D. brevis lives deeper in the sebaceous glands. A 2014 study by North Carolina State University researchers found that 100% of adults over age 18 carry DNA evidence of these mites.These organisms are incredibly small, measuring 0.15 to 0.4 millimeters in length. They are most active at night, emerging from follicles to crawl across the skin's surface at speeds of about 8 to 16 centimeters per hour. Their diet consists primarily of sebum—the oily substance produced by skin glands—and dead skin cells. Because they lack a functioning digestive tract with an anus, they accumulate waste throughout their 14-day lifespan in their large gut cells.When a mite dies, its body liquefies and releases all stored waste and bacteria onto the skin. While this sounds harmful, a healthy mite population is a normal part of the human microbiome. They play a crucial role in exfoliating skin and preventing excess oil buildup. However, if the immune system is compromised, mite populations can proliferate rapidly, potentially triggering skin conditions like rosacea or blepharitis.