Glycerin

The full Regimen Lab Skincare Encyclopedia Entry for Glycerin is in development. Check back in a few weeks for an update!

What is Glycerin?

Glycerin is discovered by Swedish scientist, C. W. Scheele discovered in 1779. Glycerin is also referred to as glycerol. It is a clear, colorless, odorless, syrupy, and hygroscopic liquid that could be made from a hydrosylate of olive oil. It is about 0.6 times as sweet as cane sugar and it is miscible with water and alcohol, slightly soluble in acetone and practically insoluble in ether and chloroform (1). It is  one  of the  most  widely  utilized  compounds  in  cosmetic  formulations because of its effects on multiple targets and its universal applications.  Its  chemical  structure  brings  together  the  stability  of three  carbon  atoms  with  three  water‐seeking  oxygen  atoms  in an anisotropic molecule that is perfectly designed for use in skin and hair moisturizers.

Glycerin and its Cosmeceutical Benefits

Glycerin has a very well established importance in skincare products. Early studies have focused on its humectant and protecting properties. More recently, glycerin has been shown to modulate the phase behavior of stratum corneum lipids and to prevent crystallization of their lamellar structures in vitro at low, relative humidity (2). Incorporation of glycerin into a stratum corneum model lipid mixture enables the lipids to maintain the liquid crystal state at low humidity (2).

Glycerin is generally classified as a humectant; however, this characteristic is not the sole reason  for  its  ability  to  achieve  skin  moisturization,  in  fact,  it performs  a  number  of  different  functions  that  are  not  directly related to its water‐holding properties. It also allows for the construction of different product physical forms that cover the spectrum from sticks  to  microemulsions  to  free‐flowing  creams  that  maintain stability over time. The degree of purity to which glycerin can be manufactured not  only  ensures  consistency  and  facilitates  microbiologic  stability, but also guarantees the minimization of allergic reactions by  contaminants.  The  pure  form  of  glycerin  has  been  tested on  thousands  of  patients  and  millions  more  have  used  it  with extremely few reports of ill effects.

What are its benefits on the skin?

Glycerin  can  restore  the  suppleness  of  skin  without  increasing  its  water  content,  a  trait  that  is  exploited  by  its  use  in  the cryopreservation  of  skin,  tissue,  and  red  blood  cells,  where water  would  freeze  and  damage  them.  It  enhances  the cohesiveness of the intercellular lipids when delivered from high glycerin therapeutic formulations, thereby retaining their presence and function. Furthermore, glycerin has been identified as a contributor to the process of desquamation, a critical component of the dermal renewal cycle, through its ability to enhance desmosome digestion. (3)

Glycerin  remains  the  gold  standard  for  moisturization.  It is a  prime  candidate  for facial moisturizer formulations due to the fact  that  it  acts  on  so  many  different  parameters  with  a  nearly non‐existent  side‐effect  profile . It is also an excellent example of how moisturizer components, especially those used on the face, should be considered for their ability to enhance and protect the skin. Glycerin raises the bar for moisturizers in that it is capable of enhancing, or even rescuing, the intrinsic processes that are in place to maintain the orderly maturation of keratinocytes and the barrier function of the skin. (3)

Glycerin has been implicated in the molecular mechanism controlling keratinocyte maturation, an important aspect of normal desquamation and  barrier maintenance.  Furthermore,  its  role  in the maintenance of hydration for the proper functioning  of  proteases,  especially filaggrin, is critical to the successful treatment of eczemas (7,8). In general, the maintenance of  the  SC  along  with  rapid  repair  of  disruptions  to  the  barrier that would otherwise become larger and increase inflammation and discomfort as well seem to be central tenets in the approach to treating potential dermatoses on the face with moisturization. Therefore, facial moisturizers may represent a valuable first‐line treatment option for many dermatologic diseases and confer a number  of  important  therapeutic  benefits  that  go  beyond  the surface of the facial skin and have a critical role in the molecular mechanisms that maintain healthy skin.

Other medicinal benefits of Glycerin

Glycerin can be used as a solvent, plasticizer, sweetener, lubricant, and preservative (4). The  substance  has  also  been  given  intravenously  or  by  mouth  in  a  variety  of  clinical conditions  in  order  to  benefit  from  its  osmotic  dehydrating  properties (5).  This  effect can also be used topically for the short-term reduction of vitreous volume an intraocular pressure of the eye (5). Concentrated solutions of glycerin is also used to soften ear wax (6). Suppositories with glycerin can also promote fecal evacuation (5, 6).

Clinical Studies:

In  addition  to  its  direct,  humectant  effects  on  skin  moisturization,  endogenously  produced  glycerin  has  exhibited  effects at  the  molecular  level  in  knockout  mouse  model  studies,  confirming its role in maintaining SC hydration and barrier maintenance. A recent study showed that glycerin content was three times  lower,  SC  hydration  was  reduced,  and  barrier  function was impaired in mice deficient in the water/glycerin transporter protein,  aquaporin‐3  (AQP3)  despite  normal  SC  structure, protein–lipid composition and ion–osmolyte content. Glycerin, but  not  other  small  poly  glycols,  restored  normal  SC  moisturization  and  TEWL  values  when  applied  to  the  AQP3‐deficient mice, confirming that glycerin was physiologically necessary in the modulation of SC hydration and barrier maintenance (9).

In vitro studies (10) have also shown that dry skin is generally stiffer than normal skin, and effective treatments such as with glycerin can indeed soften the skin. Extensive experimentation with glycerin (11) has shown that it  moisturizes dry skin in a dose-related relationship dependent on the concentration of glycerin. It was postulated that the water- glycerin mixtures on the skin also assist in plasticizing the stratum corneum in a less than transient manner.

1 Budavari S. The Merck Index Rahway: Merck & Co., Inc., 1989

2 Froebe CL, Simion A, Ohlmeyer H, et al. Prevention of stratum corneum lipid phase transitions in vitro by glycerol—an alternative mechanism for skin moisturization. J Soc Cosmet Chem 1990; 41:51–65.

3 Draelos ZD Cosmetic Dermatology Second Edition, 2010

4 American Pharmaceutical Association and The Pharmaceutical Society of Great Britain. Handbook of Pharmaceutical Excipients. Baltimore: The Pharmaceutical Press, 1986

5 Reynolds  JEF.  Martindale:  The  Extra  Pharmacopoeia.  London:  The  Pharmaceutical Press,1993.

6 Zimmerman DR. The Essential Guide to Nonprescription Drugs. New York: Harper & Row, 1983.

7 Hanifin JM. (2008) Filaggrin mutations and allergic contact sensitization. J Invest Dermatol 128, 1362–4.

8 Presland RB, Coulombe PA, Eckert RL, et al. (2004) Barrier function  in  transgenic  mice  overexpressing  K16,  involucrin,  and  filaggrin in the suprabasal epidermis. J Invest Dermatol 123, 603–6.

9 Hara M, Verkman AS. (2003) Glycerin replacement corrects defective skin hydration, elasticity, and barrier function in aquaporin-3-deficient mice. Proc Natl Acad Sci USA 100, 7360-5

10 Missel PJ, Bowman WD, Benzinger MJ, Albright GB. An in vitro method for skin

preservation to study the influences of relative humidity and treatment on stratum

corneum elasticity. Bioeng Skin 1986; 2:203–214.

11 Bissett, D.L. and McBride, J.F. (1984) Skin conditioning with glycerol. J. Soc. Cosmet Chem. 35 345-350.