Normally, I’d say it’s a bad idea to put any kind of acid on your face or body. But if you start reading the labels on your favorite health and beauty products, you’ll probably run into this one: stearic acid.
Stearic acid is a saturated fatty acid, also known as octadecanoic acid. (That’s a mouthful and a half, so I’ll stick with calling it “stearic acid” thank you very much!)
Fatty acids are a good thing for the body. They are the acids produced when fats are broken down. Fatty acids are not highly soluble in water and can be used for energy by most types of cells. Fatty acids are essential for a healthy diet, and are popular in health and beauty products, too.
Where can you find stearic acid? All over the house, actually. Soaps, cosmetics, and lotions may contain stearic acid. Stick deodorants often contain stearic acid, too! Candles may use stearic acid as well. Head for the kitchen and you might find stearic acid in vegetable oils and animal fats. It is also used in the production of margarine and shortening.
So why is stearic acid so popular? It’s a very versatile additive. It can be used as a lubricant (reducing friction by making surfaces smooth or slippery), an emulsifier (allowing oils and water to mix), and a hardener (making things resistant to pressure). For candlemakers, stearic acid makes candles harder and less likely to drip. Stearic acid can also increase the melting point, making candles last longer. It helps to harden soaps and candies, too!
And for the record? Calling something an “acid” refers mainly to the pH level — less than 7.0. There are some kinds of acid that can be harmful if used improperly, but stearic acid is perfectly safe for use in cosmetic, food, and household products.