Treat Your Feet
Why: You've been good about going to the gym. But you left your flip-flops at home. "In the last two years, I've seen a major increase in foot fungus," says Suzanne Levine, a podiatric surgeon in New York City who attributes the rise to the increased popularity of spas and health clubs. You don't just develop fungus, she says; it has to be introduced from an outside source, such as contaminated nail clippers or a dirty shower floor. "People with hyperhidrosis [excessive sweating], who constantly feel like their feet are swimming in their shoes, are more prone to fungus," says Levine.

The fix: If you've already contracted a fungus, ask your doctor for prescription-strength antifungal topicals, such as Lamisil or Penlac. Over-the-counter products are rarely strong enough, says Levine. And in the warm weather, why not give yourself the pretty punctuation of a bright polish with a pedicure? (To be safe, bring your own tools.)