Commonly-used ingredient that has multiple functions in cosmetics, including as a texture 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. The U.S. Food and Drug Administration (FDA) has even determined that butylene glycol is safe as a food additive.
References for this information:
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]
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
Journal of the American College of Toxicology, 1985, issue 2, pages 223-248