Commonly-used ingredient that has multiple functions in cosmetics, including as a slip agent and a penetration enhancer. It’s similar to propylene glycol, but has a lighter texture. The Cosmetic Ingredient Review board has evaluated several toxicology tests and other research concerning butylene glycol and has determined it is safe as used in cosmetics products. [1, 2] The U.S. Food and Drug Administration (FDA) has even determined that butylene glycol is safe as a food additive. 
- Cosmetic Ingredient Review Expert Panel. Final Report of the Cosmetic Ingredient Review Expert Panel: Amended Safety Assessment of Cocos Nucifera (Coconut) Oil, Coconut Acid, Hydrogenated Coconut Acid, Hydrogenated Coconut Oil, and its Derivatives. [Internet]. 2008 [cited 2015 July].
- Final Report on the Safety Assessment of Butylene Glycol, Hexylene Glycol, Ethoxydiglycol, and Dipropylene Glycol. JAm Coll Toxicol 1985; 2:223–248.
- Code of Federal Regulations. 21CFR172.712. [Internet]. [cited 2015 October] Available from: http://www.accessdata.fda.gov/scripts/cdrh/cfdocs/cfcfr/CFRSearch.cfm?fr=172.712&SearchTerm=butylene%20glycol