Most people experience occasional skin issues like an itch, redness, or swelling that fade quickly. These are usually harmless and linked to insect bites or irritations. Rarely, however, persistent or unusual changes under the skin may signal a parasitic infection.

In 2018, a 32-year-old woman in Russia noticed a shifting bump on her face, first near her eye, then her lip. Doctors discovered it was Dirofilaria repens, a roundworm transmitted by mosquitoes. Humans are accidental hosts, so the parasite cannot reproduce inside us, but it may cause temporary movement or swelling. The worm was removed surgically, and she recovered fully.

Subcutaneous parasitic infections occur when organisms that normally infect animals find their way under human skin. Though rare, they can cause itching, swelling, redness, or crawling sensations.

Examples include onchocerciasis (river blindness) in sub-Saharan Africa, cutaneous larva migrans from hookworms in contaminated soil, loiasis (African eye worm) in West and Central Africa, swimmer’s itch from schistosome larvae in lakes, and dracunculiasis (Guinea worm disease), now nearly eradicated.

Warning signs include persistent itching, firm bumps that move, unexplained swelling, shifting red lines, or symptoms after travel to high-risk regions. Keeping a diary of changes and exposures helps doctors in diagnosis.

Doctors may use physical exams, imaging, blood tests, or biopsies to confirm infection. Treatment often involves removing the parasite or prescribing antiparasitic medication.

Prevention is simple: use insect repellent, wear protective clothing, avoid walking barefoot on soil, swim only in safe waters, and drink clean water when traveling. Researching local risks before trips is also key.

Most skin issues are harmless, but lesions that persist, grow, or move deserve medical attention. Early evaluation provides peace of mind, and awareness ensures unusual cases are caught and treated effectively.