Commonly used slip agent that has multiple functions in cosmetics, depending on the formula. 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. 
- 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]. Available from: http://www.cir-safety.org/sites/default/files/115_ buff3e_suppl.pdf.