Humectants
Humectants are water-binding substances that absorb or retain moisture. They mimic the water-binding components found naturally in the epidermis (natural moisturizing factors) and dermis (glycosaminoglycans).
Limited amounts of water are able to penetrate the epidermis from outside the body (because the skin is highly impermeable). Skin is fairly impermeable to fluids for a very good reason. If skin were completely permeable, we’d blow up into balloons if we went into a pool or shower. There’d be nothing to stop the inflow of water!
The role of humectants is to help skin attract and hold onto water, which keeps skin moist longer. Occlusive ingredients lock the moisture in by slowing down the loss of water through evaporation (Transepidermal Water Loss). Humectant ingredients in skin care products attract water from the lower layers of the epidermis and the air.
These days, nearly every serum, moisturizer, and eye cream contains some humectants. Many toners too (the non-drying ones).
The most popular humectants in skin care are Hyaluronic Acid, which absorbs 1,000 times its molecular weight in water, and Sodium PCA, which absorbs its weight 250 times.
Common Humectants in Skin Care Products
- sodium hyaluronate / hyaluronic acid
- sodium PCA
- sodium lactate / lactic acid
- glycerin
- propylene glycol
- butylene glycol
- pentylene glycol
- propanediol
- hexanediol
- urea
- sorbitol
- betaine
- amino acids
- glucosamines
- hydrolyzed proteins (e.g. wheat protein)
- hydrolyzed collagen
- hydrolyzed elastin
- algae
- beta glucan
- colloidal oatmeal
- honey
- ceramides
- phospholipids