This fancy sounding ingredient is actually a byproduct of when you ferment soybeans. Essentially, “it’s created when lots of glutamic acid molecules (an amino acid) are linked together,” notes board-certified dermatologist Hadley King, M.D. If that sounded too science-jargony, here’s the breakdown: Amino acids are organic compounds that are the building blocks of proteins in both plants and animals. “Amino acids play an instrumental role in many ways,” says board-certified dermatologist Keira Barr, M.D. “They’re involved in many chemical reactions throughout your body to help maintain your body’s normal functions, including that of your skin.”
For this reason, they are utilized in skin care—but there are many types of amino acids that are extracted from several different sources (for skin care, the two most common sources are soy and quinoa). When used topically, they can have a variety of functions: Some act as an antioxidant and neutralize free radicals, some encourage your body to make its own antioxidants, and others help transport water, effectively acting as a hydrator.
This ingredient falls into the last category as a humectant; humectants are classes of hydrators that work by drawing in and holding onto water molecules. “Polyglutamic acid is a powerful humectant that can hold four times more water than hyaluronic acid,” says King. Hyaluronic acid, for reference, holds up to 1,000 times its weight in water.