Propylene Glycol is a humectant and humidifying agent. This ingredient is generally used in brake fluid, anti freeze, laundry detergents, paints and floor wax. It is also used in the cosmetic industry and in some foods to keep products from melting or freezing in extreme temperatures by maintaining a balanced moisture content. Propylene glycol is on the US Food and Drug Administration’s list of ingredients which are Generally Recognized As Safe (GRAS) and is recognized by the World Health Organization as safe for use.
Despite its GRAS status there are a growing number of grass roots claims that propylene glycol is an inappropriate ingredient for cosmetics and food. This is largely due to the material safety data sheet (MSDS). An MSDS is a safety disclosure which instructs manufacturers and shippers on proper procedures for handling ingredients, for treating accidental exposure, and for cleaning up spills. An MSDS does not indicate how the ingredient will react when combined with other ingredients, and the effects of exposure to any hazardous substance depend on the dose, the duration, how you are exposed, personal traits and habits, and whether other chemicals are present. However the MSDS can be used as a guide of the ingredients potential for hazard.
The material safety data sheet for propylene glycol states that it is “implicated in contact dermatitis, kidney damage and liver abnormalities; can inhibit cell growth in human tests and can damage cell membranes causing rashes, dry skin and surface damage”. The concentrated form of the ingredient can cause temporary reddening, stinging or swelling when it comes in contact with the eyes or skin. Propylene glycol is a petroleum plastic that can easily penetrate into the deeper layers of the skin potentially weakening cellular structure.
These indications do not mean that a product formulated with the ingredient will have irritating properties but that it could. Due to the potential for Propylene glycol to weaken cellular structure it is likely that people with a propensity to sensitive, easily irritated or damaged skin are more likely to be affected. However, it is probably best to avoid any cosmetic ingredient that has these risk factors as there are always safe alternatives.
If there is any good news it is that the MSDS for the propylene glycol contains no indications of carcinogenicity or chronic exposure effects and tests both in humans that have worked with this substance and animals have confirmed this. However, there are good natural alternatives to propolene glycol and in this author’s opinion, synthetic ingredients should always be avoided where possible.