What is "humectant"

Humectant \Hu*mec"tant\, a. [L. humectans, p. pr.] Diluent. -- n. A diluent drink or medicine. [Obs.]

n. any substance that promotes the retention of water, especially one used to keep a food product moist

n. any substance that is added to another substance to keep it moist

A humectant is a hygroscopic substance used to keep things moist; it is the opposite of a desiccant. It is often a molecule with several hydrophilic groups, most often hydroxyl groups; however, amines and carboxyl groups, sometimes esterified, can be encountered as well (its affinity to form hydrogen bonds with molecules of water is the crucial trait). They are used in many products, including food, cosmetics, medicines and pesticides.

A humectant attracts and retains the moisture in the air nearby via absorption, drawing the water vapor into and/or beneath the organism/object's surface. By contrast, desiccants also attract ambient moisture, but adsorb—not absorb—it, by condensing the water vapor onto the surface, as a layer of film.

When used as a food additive, a humectant has the effect of keeping the foodstuff moist.

Humectants are sometimes used as a component of antistatic coatings for plastics.

In pharmaceuticals and cosmetics, humectants can be used in topical dosage forms to increase the solubility of a chemical compound's active ingredient(s), increasing the active ingredients' ability to penetrate skin, and/or its activity time. This hydrating property can also be needed to counteract a dehydrating active ingredient (e.g., soaps, corticoids, some alcohols, etc.). This is why humectants are common ingredients in a wide range of cosmetic and personal care products that make moisturization claims (e.g., hair conditioners, body lotions, face or body cleansers, lip balms, eye creams, etc.).