As you prep your skincare regimen against another harsh winter, don’t—and we can’t emphasize this enough—forget about your fingernails. They’re easy to overlook, but your nails do a lot to serve your overall health, which is why you should take good care of them.

“If the appearance of the skin is a window into a person’s internal health, the nails are at least a porthole,” says Tyler Hollmig, M.D., director of dermatologic surgery and laser and cosmetic dermatology at the University of Texas Dell Medical Center.