Real talk: Most of the time, when a person's extremities turn a dark shade of purple out of nowhere, it's not good—life threatening, even. But for one teenage girl, that terrifying symptom turned out to be pretty harmless—and extremely strange.

A new case report from the Annals of Emergency Medicine tells the story of a 13-year-old patient whose left big toe turned a deep shade of purple. While the girl wasn't experiencing any symptoms like pain, numbness, weakness, or any past trauma to the toe, she still booked it to the emergency room because, hello, her toe was purple. During the visit, doctors didn't notice any "motor deficits," meaning her toe wasn't paralyzed. Overall, multiple tests showed "no abnormalities."

purple-toe Annals of Emergency Medicine

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Then, the patient mentioned what seemed to be a minor detail at first: She had recently found a millipede in her shoe. It turns out, that information was pretty important: The girl was ultimately diagnosed with what's known as millipede staining. (Yep, really).

A little science lesson for those of you who aren't up on your arthropod studies: Millipedes—which are typically brown in color and have lots of tiny appendages—essentially look like worms with legs. While millipedes don't bite or sting, they do release a fluid from their glands that can cause a “painless hyperpigmentation,” the case report says. “Contact with the toxic fluids can cause an acute inflammatory reaction and various forms of pigmentation or discoloration.”

According to the U.S. National Library of Medicine, the toxins that millipedes release keep them safe from most predators. In fact, some larger millipedes can spray these toxins up to 32 inches (just over 2.5 feet) away from them.

purple-toe Annals of Emergency Medicine

So, does millipede staining look really freaky? Yes, 100 percent. But it's not harmful. “Treatment includes the use of soap and water, as well as application of tape to remove any leftover millipede hairs,” the case report says. Steroids might be used to treat systemic symptoms, it adds. The case report says the application of alcohol to the skin can dissolve the toxins that cause the pigmentation.

Definitely something to keep in mind if you ever come across a millipede and then notice one of your appendages turning a deep shade of purple. (But really, even if that exact chain of events happens, it's still not the worst idea to go see a doc, just to be safe.)

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