Panthenol is the biologically active alcohol analogue of pantothenic acid, a vitamin of the B-complex group, which is a normal constituent of skin and hair. Pantothenic acid, also called Vitamin B5, carries out its function in the body as an element of co-enzyme A, a molecule composed of cysteamine, ATP, and pantothenic acid. This substance is present in all living cells and serves a vital role in the metabolism of a variety of enzyme-catalyzed reactions by which energy is released from carbohydrates, fats, and proteins.

Skin manifestations of pantothenic acid deficiency are well known, and include cornification, depigmentation, and desquamation. Pantothenic acid is an unstable substance. In topical preparations such as skincare, haircare, nailcare, and derma products, pantothenic acid is used in the alcohol form, called panthenol. Its use is based on its dual role as a vitamin precursor and as an ingredient with ideal cosmetic properties. When topically applied, panthenol is absorbed by the skin and can be bioconverted into pantothenic acid. As such it exerts all functions of
vitamin B₅.

Because it has a distinct humectant character, panthenol acts as a skin moisturizer. This hygroscopic substance not only provides water to the skin surface but it also penetrates deep into the epidermis and brings water to, and retains water in, the inside of the skin. Panthenol imparts a smooth, light feel to the skin without any greasiness or stickiness. Because it is well tolerated by the skin, it is an ideal and widely used ingredient in baby care products as well as in products for sensitive skin.
Topically applied panthenol stimulates epithelization as was shown by Weiser and Erlemann. Superficial wounds treated with creams containing 5% panthenol reduced the healing time by 30% compared with placebo. Favorable effects were also reported in many kinds of skin disorders accompanied by inflammatory reactions such as burns, nipple fissures, eczemas, and many others. Another application field of panthenol is, therefore, derma products for wound healing and for soothing of inflammatory disorders where it is usually incorporated in concentrations of 5%. The concentrations in cosmetics vary mainly from 0.3 to 2%.

The use of panthenol in haircare products goes back to the early 1960s, when inflammatory reactions on the scalp were treated with panthenol-containing creams. Panthenol not only showed a soothing effect but also had beneficial effects on the hair. Pantothenic acid is a natural constituent of human hair. Stuettgen applied tritium-labeled panthenol intracutaneously by injection and could show a transport of radioactive material into the hair. Stangl observed a significant increase of pantothenic
acid concentration in the hair after topical application of panthenol over longer periods.

Panthenol acts as a humectant for hair. It builds up a thin moisture film on the surface of the hair and gives hair shine without making it greasy. Panthenol also penetrates
into the hair cuticle and brings moisture to the cortex. This imparts good pliability and manageability properties to the hair, and improves its resistance to mechanical stress such as combing, brushing, and heat blowdrying.

Panthenol can also contribute to give hair more body. A thickening of the hair after 2 minutes exposure to a 2% water solution of panthenol was shown by means of scanning electron microscopy.

The main commercial forms are d-panthenol, dl-panthenol, and ethyl panthenol. All these forms are soluble in e.g., water, ethanol, and propylene glycol, but insoluble in fats and oils. Ethyl panthenol is an ether and available either as d-form or a racemic mixture of d- and l-form. Biological activity has only the d-form, because only d-pantothenic acid is incorporated into coenzyme A.

Source: Handbook of Cosmetic Science and Technology - André O. Barel, Marc Paye, Howard I. Maibach