Retinols and Vitamin A's in general work by speeding up cell turnover in the outer layer of your skin. This is a good thing, however it places your skin in a vulnerable state. Less stratum corneum (outer dead skin barrier) means UV Rays can penetrate more and cause excess sun damage, so you HAVE to use sun protection while using a Retinol. Or else you're basically walking into battle without a bullet proof vest...just don't. Retinols also create inflammation of your skin barrier, so you need to

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Stop Skipping This Sunscreen (SPF 30–50) Is The MOST IMPORTANT Step tips