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Shave and exfoliate -- the day before

It's best to shave or wax 24 hours before you tan to avoid irritation, Runne says. Exfoliating your entire body with a soft cotton washcloth or loofah will "ensure an even tan." You can even use a scrub made specifically for use before self-tanning, "which won't contain any oil that will prevent your skin from absorbing tanning product," Locke says.

Also, after you tan, avoid shaving or exfoliating for another day to make sure you don't take off any color, Locke says.