A Patch Test:
Wait, a patch what? It's when you apply a new product—following the directions, of course—to a small, discreet patch of skin, like behind your ear or even on the inside of your elbow. Then, you're supposed to wait 24 hours so you can look for signs of redness or irritation. Here's why: Certain ingredients, like retinol, glycolic acid, and hydroquinone (a bleaching agent used to lighten dark spots), can irritate even normal skin types.
And that's another part of the equation: Just because you don't think you have sensitive skin—or have had a reaction yet—doesn't mean you're immune to strong active ingredients. "It's always possible," NYC dermatologist Howard Sobel, M.D., founder of Park Avenue Skin and Spa, told us. "People develop allergies throughout all stages of their lives." If you've been lucky enough to have never experienced a reaction, keep an eye out for the main, uh, red flags: Redness, swelling, and itching.
If you got a little excited and already rubbed your new cream all over, it's probably going to be fine. But if you do look in the mirror and see a pink, slightly puffy version of yourself staring back at you, just wash the area you tested with water and a gentle cleanser, and then follow up with a basic moisturizer that you've used in the past. Then, return the product—that means it's definitely a bad match.
Oh, and while we're all here talking about skin care products, check out our best derm-recommended cream you definitely need to try. Bonus: First time customer gets a 10% discount for their first order!
*Article from Glamour