A humectant /hjuːˈmɛktənt/ is a hygroscopic substance. It is often a molecule with several hydrophilic groups, most often hydroxyl groups, but amines and carboxyl groups, sometimes esterified, can be encountered as well; the affinity to form hydrogen bonds with molecules of water is crucial here.
Since hygroscopic substances absorb water from the air, they are frequently used in desiccation or for humidity buffering.
When used as a food additive, the humectant has the effect of keeping the foodstuff moist. Humectants are sometimes used as a component of antistatic coatings for plastics. Humectants are also found in many cosmetic products where moisturization is desired, including treatments such as moisturizing hair conditioners and also commonly used in body lotions.
Humectants are also used in the manufacture of some cigarettes and other tobacco products.
Humectants are also used in topical dosage forms to increase the solubility of the active ingredient, to elevate its skin penetration and increase its activity time. Humectants also elevate the hydration of the skin to minimize the dehydrating effect of some active ingredients like corticoids.
Examples of humectants include propylene glycol (E1520), glyceryl triacetate (E1518), vinyl alcohol and neoagarobiose. Others can be sugar polyols such as glycerol, sorbitol (E420), xylitol and maltitol (E965), polymeric polyols like polydextrose (E1200), or natural extracts like quillaia (E999), lactic acid, or urea.
The chemical compound lithium chloride is an excellent humectant, but is toxic.