Tiny mites – eight-legged arachnids related to spiders – live in the pores of our facial skin. They are particularly fond of the hair follicles of eyebrows and eyelashes, and the oily pores most common on the nose, forehead and cheeks. Called Demodex, the mites eat sebum, or facial oil, and colonise your face at puberty.
They crawl about your face in the dark to mate, then crawl back into pores to lay their eggs and die. Healthy adults have around one or two mites per square centimetre of facial skin. People with rosacea, however, can have 10 times as many, says Kavanagh. Research suggests that the stress that causes flare-ups of rosacea changes the chemicals in sebum, making it better food for mites.
Demodex does not have an anus and therefore cannot get rid of its faeces. "Their abdomen just gets bigger and bigger, and when they die and decompose they release their faeces all at once in the pore," says Kavanagh. When the mites are numerous, he believes that the material is enough to trigger an immune reaction, inflammation and tissue damage.
