Petrolatum beats glycerin below freezing.

Below freezing, occlusives like petrolatum are the real workhorses for preventing transepidermal water loss, and humectants like glycerin can actually backfire.

The problem with humectants in extreme cold is that they work by pulling moisture from the environment into your skin. But when it’s below freezing, the air is bone-dry—there’s almost no water vapor to grab. So glycerin ends up drawing moisture from deeper layers of your skin instead, making things worse. It can also freeze on your face if you’re outside long enough, which does nothing good.

Occlusives, on the other hand, just form a physical barrier. Petrolatum sits on top of your skin and locks the water that’s already there inside. It doesn’t need humidity to work, and it won’t freeze. That’s why old-school winterbeater balms and chapsticks are mostly petrolatum.

If you’re going to be outside for hours in subzero temps, slap on an occlusive as your last layer. Save the humectants for when you’re back inside and can apply them in a humid bathroom.

This is one time you want your face to feel a little greasy.