Safety assessment of Glycerin as Used in Cosmetics

Introduction:
This text is a safety assessment of glycerin as used in cosmetics. Glycerin is a polyhydric alcohol that functions in cosmetics as a denaturant, fragrance ingredient, hair conditioning agent, humectant, oral care agent, oral health care drug, skin protectant, skin-conditioning agent-humectant, and viscosity decreasing agent. The assessment is based on information provided by the Organization for Economic Cooperation and Development (OECD) Screening Information Data Set (SIDS), the European Commission - European Chemicals Bureau (IUCLID), and unpublished data provided by industry.

Key Points:

* Glycerin is a clear, syrupy liquid that is completely miscible with water, methanol, ethanol, and the isomers of propanol, butanol, and pentanol. It is obtained as a byproduct in the conversion of fats and oils to fatty acids or fatty acid methyl esters.
* Glycerin is rapidly absorbed in the intestine and the stomach, distributed throughout the extracellular space and renally excreted. It is metabolized by glycerokinase, predominantly in the liver and kidneys, and incorporated via standard metabolic pathways to form glucose and glycogen.
* Glycerin is reported to be used in 15,654 cosmetic products, including 10,046 leave-on products, 5441 rinse-off products, and 167 products diluted for the bath. It is used at concentrations up to 78.5% in leave-on products, 68.6% in rinse-off products, and 47% in products diluted for the bath.
* Glycerin is considered generally recognized as safe (GRaS) by the FDa for food packaging and as a multiple-purpose food substance. It is also used in over-the-counter drugs, such as anorectal drug products, dermal protectant products, ophthalmic drug products, and oral health care products.
* Glycerin is rapidly absorbed in the intestine and the stomach, distributed throughout the extracellular fluids through much of the body, and excreted in urine. The reported oral LD50 of glycerin is 2530-58400 mg/kg in rats, 4090-38000 mg/kg in mice, 27000 mg/kg in rabbits, and 77500 mg/kg in guinea pigs. The dermal LD50 of glycerin in rats is reported to be >21900 mg/kg and >18700 mg/kg in rabbits.
* Glycerin was not genotoxic in multiple ames tests, a cytogenetic assay, an X-linked hypoxanthine-guanine phosphoribosyl transferase (hGPRT) assay, a sister chromatid exchange assay using Chinese hamster ovary (ChO) cells, an unscheduled DNa synthesis assay using rat hepatocytes, or a chromosome aberration test using ChO cells.
* Glycerin administered in the feed of rats at concentrations up to 20% for 1 year or up to 10 g/kg for 2 years did not increase the incidence of tumors. however, glycerin administered in drinking water, up to 5% in as little as 4 weeks, had a synergistic effect with 4-nitroquinoline 1-oxide (4NqO) in mice.
* Glycerin was not dermally irritating in rabbits at concentrations up to 100% and was not irritating to the eyes of rabbits at concentrations up to 100%. It was not sensitizing to white male guinea pigs at 0.1%.

Main Message:
The Cosmetic Ingredient Review (CIR) Expert Panel concluded that glycerin is safe in the present practices of use and concentration described in this safety assessment in cosmetics. Glycerin is a widely used cosmetic ingredient with low oral and dermal toxicity and a high frequency of use in cosmetic products. It is not genotoxic or carcinogenic and is not a dermal or ocular irritant or sensitizer. The source materials and intermediate forms of glycerin should be completely consumed or eliminated through the distillation process. The FDa has warned against using the Jatropha species of plant for a source material and stressed that this plant should not be a source material. The potential for incidental inhalation exposure from hair sprays, deodorants, face and neck products, face powders, moisturizing products, and suntan products is low and is not expected to result in significant respiratory or systemic effects.

Becker, Lillian C., Wilma F. Bergfeld, Donald V. Belsito, Ronald a. hill, Curtis D. Klaassen, Daniel C. Liebler, James G. Marks, et al. “Safety assessment of Glycerin as Used in Cosmetics.” International Journal of Toxicology 38, no. 3_suppl (November 2019): 6S-22S. https://doi.org/10.1177/1091581819883820.