These bugs mate on your face as you sleep. Are they friends or foes?

Sign up for CNN’s Sleep, But Better newsletter series. Our seven-part guide has helpful hints to achieve better sleep. As you fall asleep each night, you can take comfort in knowing you are never truly alone — thanks to the dozens of eight-legged mites crawling out of your pores to party. You can’t see or feel these nocturnal crawlers, called demodex mites, but like almost every adult, you have them all over your body. Smaller than a pinpoint, the tiny invertebrates, which measure about 0.15 millimeters to 0.4 millimeters in length, live around the outer parts of hair follicles and feed on their oily contents. “While we are sleeping, they come out and are very happy, mating, visiting relatives, walking on our faces. The moment we wake up, they go back inside the pore,” said Alejandra Perotti, an associate professor of invertebrate biology at the University of Reading in England. If you’re creeped out, Perotti said, “don’t be.” Demodex mites are more often friends than foes. In exchange for cleaning the gunk out of our pores, we offer these miniature vacuums our melatonin, a hormone produced in the skin that puts us to sleep but gives the mites vital energy, Perotti said. And like microscopic vampires, the mites have evolved to avoid ultraviolet rays from the sun, which easily destroys their DNA. The face typically has up to five mites per square centimeter — although without putting a sample of skin under a microscope, it’s impossible to see them with the naked eye. If your immune system weakens, the mite populations can sometimes overproduce, leading to a host of skin and eye conditions. When they ‘mite’ cause problems Demodex mites can multiply overnight, causing an overgrowth called demodicosis, said Dr. Richard Locksley, professor of medicine at University of California, San Francisco. Immunodeficient individuals, such as older adults or people on chemotherapy, are more vulnerable to demodicosis and may have an inflammatory response to the mites and the bacteria that can colonize them, Locksley said. It’s not totally known why some people experience inflammation from the mites, Locksley said. “But what is known is that wild animals don’t have any diseases from the mites, but domestic dogs and cats do. So perhaps when we moved into a different environment, and the way we evolved, a genetic mutation compromised our immune pathways.” The inflammation can manifest as rosacea, acne, dryness and flaking, especially on the cheeks, eyelids, forehead and creases where oil may accumulate, said Dr. Roberto Ricardo-Gonzalez, associate professor of dermatology at University of California, San Francisco, who worked closely with Locksley to research the mites. To determine whether demodex mites are the cause of skin irritations, dermatologists can tape or lightly scrape the top layer of skin and place the sample under a microscope, Ricardo-Gonzalez said. During a routine eye exam, the doctor may check for a waxy buildup of demodex eggs and waste around the base of the eyelashes. said Dr. Cory Lappin, an Ohio optometrist. For patients with eyelid infections, this buildup is a common cause of dryness, itchiness, eyelash loss and even recurrent sties. Preventing and treating overgrowth For most healthy adults, there is no need to panic about demodex mites. “Most people are completely unaware they have the mites, and (it) should stay that way,” Locksley said. “You could do more harm picking around looking for problems than just being agnostic about it. And if you have problems, you should go talk to a physician first.” Both Lappin and Ricardo-Gonzalez recommend maintaining a regular hygiene routine before bedtime, including a gentle cleanser to remove debris and excess oil from the face. Take off eye makeup and false lashes before sleep as well to keep the area clean and avoid irritating the delicate tissue around the eye, Lappin said. Those with acne-prone skin can use a topical retinoid one or two nights a week, Ricardo-Gonzalez said, noting that moderation is key to a bedtime skin care routine. “I’ve seen it in patients when you have moisture-barrier disruption, meaning your skin is overly dry or overproducing oil from inflammation or excessive washing. The mites can overgrow in those instances,” Ricardo-Gonzalez said. Regular, adequate sleep is also important to prevent skin from overproducing sebum, the oily substance that’s like food for the mites, studies have shown. To treat demodicosis, a dermatologist might prescribe topical or oral ivermectin to reduce the populations back to normal counts, Ricardo-Gonzalez said. It’s not possible, though, to completely rid yourself of the mites permanently. The US Food and Drug Administration approved medicated eye drops in 2023 to treat demodex-related eyelid inflammation, Lappin said. Here today, gone tomorrow? Observed on humans for centuries, demodex mites are thought to be passed from contact with our mothers shortly after birth. Perotti and her research team discovered in 2022, however, that these symbiotic creatures may be experiencing what she calls “a long-term evolutionary death.” “When you have organisms that are exposed to this symbiotic life, it leads to genome erosion, or a loss of genes over time,” Perotti said. “We predict that this will continue to the point that (the mites) will disappear.” With no predators, external threats or competitors, demodex mites have no selective pressures, Perotti explained. And since they are passed down between related humans, the populations lack genetic diversity — in other words, they are inbred. It’s unknown how long the extinction will take, but to Perotti, this is nothing to celebrate — or mourn — considering humans will likely adapt to need demodex mites less as they die out. “There has been very bad talk about the mites for a long time. They have been blamed for a lot of problems, but the suppressed immune system is the problem, not the mite itself,” Perotti said. “We should think of them as our companions.”