skincare products

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Don't: Try More than 1 New Skincare Product at a Time

Why it's really that bad: The more unfamiliar ingredients and products there are on your face at once, the higher the likelihood that your skin won't play well with one of them. "And if you have a reaction, you won't know which product caused it," says Doris Day, a clinical associate professor of dermatology at NYU Langone Medical Center, in New York. The fix: Don't try to overhaul your entire skincare regimen in one go. Limit new products to 1 per day.