Minor skin irritations are often mistaken for “allergic reactions, bug bites, or harmless rashes.” Yet in rare cases, they can signal a parasitic infection living under the skin.

A striking example occurred in Russia in 2018. A 32-year-old woman noticed a bump on her face that appeared and disappeared over several days. At first, she thought it was a mosquito bite, but soon “the bump began to move—shifting from under her left eye to her upper lip” within two weeks.

Doctors later discovered it was caused by Dirofilaria repens, a parasitic worm usually found in dogs and other carnivores. Humans can become infected when bitten by mosquitoes carrying the parasite. According to the New England Journal of Medicine, the woman felt little discomfort, but the worm’s movement was visible. It was removed with minor surgery, and she recovered fully.

Dirofilaria species are roundworms transmitted by mosquitoes. In animals, they reproduce in the bloodstream, but in humans, they cannot complete their life cycle. Still, they may cause “nodules, itching, and inflammation” as they travel through tissues.

Such cases are rare, but they highlight the importance of medical attention when skin irritations seem unusual or persistent.