Thoemmes worked on a project that examined the faces of more than 4,000 people for these critters, called Demodex mites. “We haven’t found a single person without them,” she says. Demodex can live all over our bodies. But they’re most abundant on our faces, where they may eat dead cells and an oily substance called sebum. The mites are probably harmless and may even benefit us in some unknown way. “They’re just hanging out, like thousands of little friends who are always with you,” says Thoemmes.
Mites are just one of the many microscopic organisms that live on us. “The body is its own ecosystem that hosts thousands of species,” says Thoemmes. “It’s like a forest, with mites, fungi, and bacteria interacting and working together to form a community.” Many of our body’s regular residents, like the microbes in our gut that help with digestion, play important roles in keeping us healthy. But our bodies sometimes pick up problematic invaders too. Unwanted parasites like head lice can drink blood from our scalps, while certain worms can infest our intestines, robbing us of nutrients. Yikes!