I’m going to be honest and admit that I only heard about the acid mantle recently. I know it’s my job to stay current with wellness trends, but frankly, I thought it was a drug thing. In case, like me, you’ve been out of the loop, an acid mantle is the protective oily film that coats the skin and supposedly protects not just the skin, but the whole immune system. Before you sprain a muscle with your side eye, here’s what dermatologists say about the function of this mystical, invisible barrier.

“The acid mantle is a thin layer on the skin composed of a mixture of free fatty acids secreted from the oil glands mixed with lactic acid and amino acids from sweat,” says Peterson Pierre, a California-based dermatologist. That’s a lot of complicated science words, so for liberal arts grads, it’s the slight film you feel on the surface of your skin most of the time, says Rachel Liverman, an esthetician and co-founder of Glowbar, a skin treatment boutique in NYC.

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