A humectant hjuːˈmɛktənt is a hygroscopic substance

Chemical substance

In chemistry, a chemical substance is a form of matter that has constant chemical composition and characteristic properties. It cannot be separated into components by physical separation methods, i.e. without breaking chemical bonds. They can be solids, liquids or gases.Chemical substances are...

. It is often a molecule with several hydrophilic groups, most often hydroxyl groups, but amine

Amine

Amines are organic compounds and functional groups that contain a basic nitrogen atom with a lone pair. Amines are derivatives of ammonia, wherein one or more hydrogen atoms have been replaced by a substituent such as an alkyl or aryl group. Important amines include amino acids, biogenic amines,...

s and carboxyl groups, sometimes ester

Ester

Esters are chemical compounds derived by reacting an oxoacid with a hydroxyl compound such as an alcohol or phenol. Esters are usually derived from an inorganic acid or organic acid in which at least one -OH group is replaced by an -O-alkyl group, and most commonly from carboxylic acids and...

ified, can be encountered as well; the affinity to form hydrogen bond

Hydrogen bond

A hydrogen bond is the attractive interaction of a hydrogen atom with an electronegative atom, such as nitrogen, oxygen or fluorine, that comes from another molecule or chemical group. The hydrogen must be covalently bonded to another electronegative atom to create the bond...

s with molecules of water is crucial here.

Since hygroscopic substances absorb water

Water

Water is a chemical substance with the chemical formula H2O. A water molecule contains one oxygen and two hydrogen atoms connected by covalent bonds. Water is a liquid at ambient conditions, but it often co-exists on Earth with its solid state, ice, and gaseous state . Water also exists in a...

 from the air, they are frequently used in desiccation

Desiccation

Desiccation is the state of extreme dryness, or the process of extreme drying. A desiccant is a hygroscopic substance that induces or sustains such a state in its local vicinity in a moderately sealed container.-Science:...

 or for humidity buffering

Humidity buffering

Humidity buffering refers to the ability of materials to moderate changes in relative humidity by absorbing and desorbing water vapour from surrounding air. This is also referred to as moisture buffering....

.

When used as a food additive

Food additive

Food additives are substances added to food to preserve flavor or enhance its taste and appearance.Some additives have been used for centuries; for example, preserving food by pickling , salting, as with bacon, preserving sweets or using sulfur dioxide as in some wines...

, the humectant has the effect of keeping the foodstuff moist. Humectants are sometimes used as a component of antistatic coatings for plastic

Plastic

A plastic material is any of a wide range of synthetic or semi-synthetic organic solids used in the manufacture of industrial products. Plastics are typically polymers of high molecular mass, and may contain other substances to improve performance and/or reduce production costs...

s. Humectants are also found in many cosmetic products where moisturization is desired, including treatments such as moisturizing hair conditioner

Hair conditioner

Hair conditioner is a hair care product that alters the texture and appearance of hair.-History:For centuries, natural oils have been used to condition human hair. These natural products are still used today, including essential oils such as tea tree oil and carrier oils such as jojoba oil...

s and also commonly used in body lotions.

Humectants are also used in the manufacture of some cigarettes and other tobacco

Tobacco

Tobacco is an agricultural product processed from the leaves of plants in the genus Nicotiana. It can be consumed, used as a pesticide and, in the form of nicotine tartrate, used in some medicines...

 products.

Humectants are also used in topical

Topical

In medicine, a topical medication is applied to body surfaces such as the skin or mucous membranes such as the vagina, anus, throat, eyes and ears.Many topical medications are epicutaneous, meaning that they are applied directly to the skin...

 dosage form

Dosage form

-Introduction:Dosage forms are a mixture of active drug components and nondrug components. Depending on the method of administration they come in several types. These are liquid dosage form, solid dosage form and semisolid dosage forms. A Liquid dosage form is the liquid form of a dose of a...

s to increase the solubility of the active ingredient

Active ingredient

An active ingredient is the substance of a pharmaceutical drug or a pharmaceutical ingredient and bulk active in medicine; in pesticide formulations active substance may be used. Some medications and pesticide products may contain more than one 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

Propylene glycol

Propylene glycol, also called 1,2-propanediol or propane-1,2-diol, is an organic compound with formula C3H8O2 or HO-CH2-CHOH-CH3...

 (E

E number

E numbers are number codes for food additives that have been assessed for use within the European Union . They are commonly found on food labels throughout the European Union. Safety assessment and approval are the responsibility of the European Food Safety Authority...

1520), glyceryl triacetate (E1518), vinyl alcohol and neoagarobiose. Others can be sugar polyol

Sugar alcohol

A sugar alcohol is a hydrogenated form of carbohydrate, whose carbonyl group has been reduced to a primary or secondary hydroxyl group . Sugar alcohols have the general formula Hn+1H, whereas sugars have HnHCO...

s such as glycerol

Glycerol

Glycerol is a simple polyol compound. It is a colorless, odorless, viscous liquid that is widely used in pharmaceutical formulations. Glycerol has three hydroxyl groups that are responsible for its solubility in water and its hygroscopic nature. The glycerol backbone is central to all lipids...

, sorbitol

Sorbitol

Sorbitol, also known as glucitol, Sorbogem® and Sorbo®, is a sugar alcohol that the human body metabolizes slowly. It can be obtained by reduction of glucose, changing the aldehyde group to a hydroxyl group. Sorbitol is found in apples, pears, peaches, and prunes...

 (E420), xylitol

Xylitol

Xylitol is a sugar alcohol sweetener used as a naturally occurring sugar substitute. It is found in the fibers of many fruits and vegetables, and can be extracted from various berries, oats, and mushrooms, as well as fibrous material such as corn husks and sugar cane bagasse, and birch...

 and maltitol

Maltitol

Maltitol is a sugar alcohol used as a sugar substitute. It has 75-90% of the sweetness of sucrose and nearly identical properties, except for browning. It is used to replace table sugar because it has fewer calories, does not promote tooth decay, and has a somewhat lesser effect on blood glucose...

 (E965), polymeric polyol

Polyol

A polyol is an alcohol containing multiple hydroxyl groups. In two technological disciplines the term "polyol" has a special meaning: food science and polymer chemistry.- Polyols in food science :...

s like polydextrose

Polydextrose

Polydextrose is an indigestable synthetic polymer of glucose. It is a food ingredient classified as soluble fiber by the U.S. Food and Drug Administration , but not Health Canada. It is frequently used to increase the non-dietary fiber content of food, replace sugar, reduce calories and reduce fat...

 (E1200), or natural extracts like quillaia

Quillaia

Quillaia is the milled inner bark or small stems and branches of the soapbark . Other names include China bark extract, Murillo bark extract, Panama bark extract, Quillai extract, Quillaia extract, Quillay bark extract, and Soapbark extract...

 (E999), lactic acid

Lactic acid

Lactic acid, also known as milk acid, is a chemical compound that plays a role in various biochemical processes and was first isolated in 1780 by the Swedish chemist Carl Wilhelm Scheele. Lactic acid is a carboxylic acid with the chemical formula C3H6O3...

, or urea

Urea

Urea or carbamide is an organic compound with the chemical formula CO2. The molecule has two —NH2 groups joined by a carbonyl functional group....

.

The chemical compound lithium chloride

Lithium chloride

Lithium chloride is a chemical compound with the formula LiCl. The salt is a typical ionic compound, although the small size of the Li+ ion gives rise to properties not seen for other alkali metal chlorides, such as extraordinary solubility in polar solvents and its hygroscopic...

is an excellent humectant, but is toxic.