Propylene Glycol can be a skin sensitizer and can instigate immune system response that can include itching, hives, scaling and blistering of the skin. A sweet colorless, viscous, hygroscopic liquid used as an antifreeze and in brake fluid and also as a humectant in cosmetics and personal care items although it may be absorbed through the skin with harmful effects. It is a synethic petrochemical that can be quickly aborbed through the skin. It is a strong irritant that may cause acne, contact dermatitis and delayed allergic reactions.
NIOSH say neurotoxin, may cause kidney, liver damage; EPA says not fully investigated for carcinogenic potential; CIR says safe if equal/less than 50%.