A couple who had itchy, red rashes on their stomachs discovered they’d been bitten by mites that were the parasites of beetles living in their furniture.
The 30-year-old man and woman from France went to an infectious disease clinic to be checked out three days after the rashes appeared on their skin, according to the authors of a case report published in the New England Journal of Medicine in June.
The team treating them suspected that the couple’s home had an infestation. Their furniture was inspected and common furniture beetles, which bore through wood, were discovered.
Knowing that these beetles can have their own parasites, called Pyemotes ventricosus mites, the team were able to diagnose the couple’s rashes — including the woman’s, which was comet-shaped — as dermatitis caused by bites from the mites.
Co-author Dr. Philippe Parola, a professor of infectious diseases and tropical medicine at Aix-Marseille University, France, told Insider that a comet-shaped rash occurs in one quarter of cases where humans have reactions to bites from Pyemotes ventricosus mites.
It’s very rare for these parasites to bite humans
The mites, also known as European straw itch mites, aren’t visible to the human eye, and their bites are painless, so the couple had no way of knowing what the marks were from.
It’s quite unusual for these mites to bite humans, with only 40 known case reported since the first in 1909. Female European straw itch mites inject a toxin into their prey, which paralyzes it as the mite feeds on it.
The mite then births up to 300 adult mites, which immediately go and find their own prey. If there aren’t enough beetles around to feed the mites, they will bite any mammals available, including humans.
If they do bite humans, usually the only symptom is the itchy rash, although in rare cases people experience fevers and vomiting. People who work closely with wooden furniture, wheat, grain, grasses or dried beans are most likely to be bitten.
In this case, the mites had parasitized the wood-boring beetles that were infesting the couple’s furniture.
Bites are only easily identified if they are comet-shaped, but the rash is easy to treat
Not all European straw itch mite bites show up in the telltale comet shape. If the large pink marks don’t have tails, it can take doctors longer to identify them. But when they do, they can be treated pretty easily, or they go away by themselves within one to three weeks.
The couple were treated with topical steroids and antihistamines, got rid of their infested furniture, and their itchy rashes disappeared within eight days.