Propanediol
1,3-Propylene Glycol,
1,3-Dihydroxypropane,
1,3-Propanediol,
Zemea Propanediol
Formula: C3H8O2
Molecular Weight: 76.09
Cas No:504-63-2; 26264-14-2
Solvent; Viscosity Controlling

http://www.paulaschoice.com/cosmetic-ingredient-dictionary/definition/propanediol
"A glycol that can enhance the absorption of ingredients (such as salicylic acid) into the skin. Propanediol can be derived naturally (from corn) or synthetically. It has hydrating properties that may leave a smooth, dewy finish. Propanediol is a well-tolerated ingredient, not likely to cause sensitivity."