Dandruff shampoo

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Dandruff Shampoo
Standard use: Keeping heads and shoulders flake-free.

Surprise use: Helping to clear up discolored patches that appear on the back, underarms, upper arms, chest and neck (they're reddish-tan on light skin and white on darker skin).

This relatively common rash is actually a skin fungus known to dermatologists as tinea versicolor, and while it can be stubborn, it usually responds well to this treatment. "Choose a shampoo that contains selenium sulfide, then lather up the affected area, let it sit for about 10 minutes, and rinse," says Neuhaus (you can treat your scalp and your skin at the same time). You should see results in about a week.