If your complexion is suddenly greasy and broken out, red and blotchy, or dry and flaky, there are, of course, the usual suspects to blame: your period (high androgen levels can cause pimples), stress (anxiety stokes inflammation in the skin, spurring acne), or a night of not enough zzz’s (which ups stress and interrupts skin repair). But beyond those, there are more mysterious things that can lead your skin to rebel out of the blue, things the pros look for—and now you will, too. For instance, when his patients who travel routinely returned complaining of skin issues, Dennis Gross, M.D., a dermatologist in New York City, began questioning whether the different tap water could be at play. Sure enough, he discovered that what comes out of your faucet can dictate…
