First up: It’s an ingredient with very few cautions attached. This is because it’s gentle, and allergies to it are very, very rare. “Thankfully there isn’t too much sensitivity or allergies with the use of glycerin,” says Farhang.
The best way to use glycerin is to, well, use products previously formulated with it. (Unlike some of our other favorite natural ingredients, there are not too many DIY opportunities here.) “The best way to use glycerin is in a skin care product that contains it, along with other hydrating ingredients that help hold moisture in your skin,” says Cochran Gathers. “I don’t recommend mixing up your own glycerin facial moisturizers.”
So let’s say you’ve found your product du jour—any application tips? As with other humectants, “When you apply your moisturizing products with glycerin, apply them to mildly damp skin,” says Cochran Gathers. This is because humectants need water to attract and hold on to in the first place—if you apply them on dry skin, you run the risk of the ingredient pulling water from lower layers of the dermis to the top, where it can evaporate into the air. Glycerin should also be combined with other ingredients, like emollients and occlusives, to help trap the water in the skin. “Over-the-counter glycerin-containing products can typically be used a few times a day to help moisturize your skin,” she notes as well.