Proponents quote and maintain studies showing it to be a safe, effective ingredient.
On the skin, it gives a smooth, greasy feel, but it does so by replacing and repelling important components necessary for healthy skin. While binding moisture, propylene glycol also repels moisture. It therefore acts as a replacement for water, but the skin cannot utilize it. Skin functions on water, not anti-freeze. This report showed propylene glycol to cause a significant number of reactions and was a primary irritant to the skin even in low levels of concentration.