Glycerine combined with alcohol to form a syrupy humectant. When used in make-up, it helps the foundation adhere to the skin. Propylene glycol is one very commonly used synthetic glycol. Some others are ethylene glycol, diethylene glycol, and carbitol. Most glycols are synthetic and toxic.
Glycols (Wikipedia)
A diol is a chemical compound containing two hydroxyl groups (−OH groups). An aliphatic diol is also called a glycol. This pairing of functional groups is pervasive, and many subcategories have been identified.
Ethylene glycol, a common diol
The most common industrial diol is ethylene glycol. Examples of diols in which the hydroxyl functional groups are more widely separated include 1,4-butanediol HO−(CH2)4−OH and propylene-1,3-diol, or beta propylene glycol, HO−CH2−CH2−CH2−OH.
