By Angela Haupt

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A dark streak under your toenail

Mirza recently diagnosed a patient with subungual melanoma, a rare type of skin cancer that develops under the nail bed. The telltale sign is a dark vertical line that can also lead to other color changes in or around the nail. Get in the habit of doing regular self-checks, she urges; if you typically wear nail polish, which would conceal any discoloration, check your toes before reapplying a new coat. If anything looks different than usual, schedule a doctor’s appointment.

Subungual melanoma is curable when it’s detected in an early stage. While treatment depends on the stage of the cancer, it might include removing the nail or amputating the toe in some cases. “The goal is to not have to remove the entire toe, but it depends how soon you catch it,” Mirza says.

Numbness or tingling in the feet

Sharkey’s patients sometimes show up with symptoms that indicate metabolic problems—like numbness, tingling, or burning in their feet that gets worse at night. “During the day, our body is processing so much external feedback,” she says. “At night, when things are quiet, all of a sudden your body is so much more aware.” What your body might be saying: “‘My toes are tingling, or they feel like they’re on fire,’” Sharkey says.