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Humectants and Cosmetics
Humectants play a large role in cosmetics, particularly in lotions and cleansers because of their moisturizing abilities. A humectant is a substance that preserves and locks in moisture. Humectants attract water to the stratum corneum, or the outermost layer of the skin [1 ]. The humectant does this by obtaining water from the inner layer of the dermis and moving it to the outer layer, resulting in a moisturized feeling of the skin. Once humidity of the atmosphere has passed 70%, humectants can capture water from the atmosphere into the epidermis [2 ]. By attracting water from both the under layer of the skin and the atmosphere, humectants are able to thoroughly hydrate the skin. Humectants not only allow, but also assist in the shedding of the outer layers of the skin by eliminating the part of the skin called the corneodesmosomes that keeps the skin together [3]. By assisting in the shedding of skin, humectants allow for the more healthy skin become the predominant layer. This gives an overall healthier appearance of the skin. Some benefits of humectants effect on the skin include: better absorption of moisture from the atmosphere, increased pliability and flexibility of the skin, reduced irritability of the skin, and prevention of chemicals affecting the skin. The three most common humectants in beauty products are glycerin, sorbitol, and propylene glycol [4 ]. Glycerin: The most common humectant is glycerin, which is a sugar compound. It is most often found in lotions or shampoos. When more than 5% of glycerin is used in a product a sticky residue is left on the skin [5 ]. There are no health hazards known associated with glycerin.

Sorbitol: The second most common humectant is sorbitol. It is a sugar compound most often found in toothpastes. Like glycerin there are no side effects on ones health with the use of sorbitol.

Propylene Glycol: The third most commonly found humectant in beauty products is propylene glycol. It is an alcohol-based humectant. In 1984, a study found that concentrations of propylene glycol over 50% were hazardous [6 ]. The most common place to find high concentrations of propylene glycol is in deodorant. More recent studies have determined that the highest concentration of propylene glycol before it becomes hazardous is 7.5% [7 ]. These high concentrations of propylene glycol are only hazardous when applied to the skin. When it is taken orally, there are no health hazards.

References

[1][4][5][7] Klien, K. Making Cosmetics INC. (2005). Humectants (Moisturizing Agents) [Brochure]. . Retrieved February 08, 2014, from http://www.makingcosmetics.com/

[2] Brannon, H. (N/d). Humectant. Health. Retrieved from http://dermatology.about.com/od/glossaryh/g/humectant.htm

[3] Rawlings, Anthony, et al. "Humectants." Skin Moisturization. Ed. James J. Leyden and Anthony V. Rawlings. New York: Marcel Dekker, 2002. 248-257.

[6] Monice, F. (2012). Safety assessment of propylene glycol, tripropylene glycol, and ppgs as used in cosmetics.International Journal of Toxicology, Retrieved from http://www.ncbi.nlm.nih.gov/pubmed/23064775