Glycerine

Buss, C. (Photographer). (2018) Hair products containing glycerine. Calgary, Canada

Glycerine is a commonly used moisturizer and sweetener found in most personal care products and is also known as glycol and glycerin¹. It is a thick, colourless liquid with a slightly sweet odour². While it’s melting point is only around 18°C, the freezing point is much lower at -38°C so glycerine works great as a cryoprotective agent².

                Unlike other commonly used antifreezes, glycerine is relatively safe. There is no evidence linking it to reproductive problems3 and there are no negative long-term effects from using it. At high doses, it can lead to seizures, lower blood levels, and dehydration but overdoses require over 3.5g/kg to be consumed²; that’s over 250 grams needed for the average grown man!

Glycerine is also usually stable but when combined with a few specific chemicals, it can be explosive. When it is mixed with nitric acid, it forms the explosive nitroglycerine which is used to make dynamite². Similarly, combining it with perchloric acid, chlorine or other strong oxidizing agents can make powerful explosive reactions². These elements and compounds are rarely found in medicines though, so there is no known reactivity between glycerine and medications⁴.

                Glycerine is made by heating up oils and fats which are composed of esters called triglycerides which are made up of glycerol and fatty acids. By heating up the triglycerides in the presence of a strong base, they break down into glycol and fatty acids which can be purified out through a boiling process⁵. This process is usually done in the soap making process where lye is used as the strong base and the glycerine is left in to act as a moisturizer⁵. Glycerine can also be made synthetically from petroleum and is a by-product of producing biofuels⁶; however, the glycerine by-product is highly contaminated and instead of purifying it, it is usually just burned or disposed of⁶.

                Glycerine is used as a moisturizer, sweetener, and antifreeze. It can be found in everything from baked goods and ice cream to skin and haircare products and hand sanitizer⁶. It acts as a barrier to prevent moisture loss and to keep air off of the skin so is also found in treatments for rashes, bites, cuts and other skin irritations⁶ as well as a sweetener in medicine⁷. It is also used in mouthwashes and toothpastes because, unlike with other sweeteners, bacteria cannot feed on it and starve which helps prevent bad breath². It is found in most E-cigarettes as well.

References:

¹NIOSH. Glycerol. https://www.cdc.gov/niosh/ipcsneng/neng0624.html (accessed December 1, 2018)

²National Center for Biotechnology Information. PubChem Compound Database; CID=753, https://pubchem.ncbi.nlm.nih.gov/compound/753 (accessed Dec 1, 2018).

³Briggs, G. Freeman, R. Drugs in Pregnancy and Lactation: A Reference Guide to Fetal and Neonatal Risk. [Online]. Wolters Kluwer Health. Philadelphia. 2015. Retrieved from  https://books.google.ca/books/about/Drugs_in_Pregnancy_and_Lactation.html?id=tkjvAwAAQBAJ&printsec=frontcover&source=kp_read_button&redir_esc=y#v=onepage&q=glycerin&f=false

⁴Cuhna, J. Glycerin. https://www.rxlist.com/consumer_glycerin/drugs-condition.htm (accessed December 1, 2018

 ⁵Stai, S. How is Glycerol Made? https://sciencing.com/glycerol-made-7489385.html (accessed December 4, 2018)

⁶ Glycerine. https://thechemco.com/chemical/glycerine/ (accessed December 1, 2018)

⁷ Glycerine. (2012). In R. Sell, M. A. Rothenberg, & C. F. Chapman, Dictionary of medical terms (6th ed.)[online]. Hauppauge, NY: Barron's Educational Series. Retrieved from https://librarysearch.mtroyal.ca/discovery/openurl?institution=01MTROYAL_INST&vid=01MTROYAL_INST:02MTROYAL_INST&https://search.credoreference.com/content/entry/barronsm/glycerine/0?institutionId=2638