Is Propylene Glycol Used As a Conditioning Agent in Shampoos?

Commercial shampoo preparations include a variety of ingredients, each with a specific purpose. Besides water and detergent, shampoos typically contain fragrances, coloring agents, conditioners, thickeners, acidifiers, lathering agents and preservatives. Propylene glycol in shampoos acts as a conditioner and a preservative.

Description

Propylene glycol is a clear, slippery liquid that can mix with water, chloroform and acetone. A type of alcohol known as a glycol or diol, is it an organic compound with two hydrogen-water components. It is hygroscopic, meaning that it attracts water. Its many other scientific names include alpha-propylene glycol, methylethyl glycol, 1,2-dyhydroxypropane and propane-1,2-diol.

Function in Shampoo

Conditioners in shampoo achieve their effects by a variety of methods. Propylene glycol acts as a humectant, or moisturizer, when applied to the hair. It coats the cuticle, which is the outer covering of the hair shaft, and keeps it moist by attracting moisture from the air. Propylene glycol also keeps mold from growing in the shampoo.

Other Uses

Industry has found a dizzying range of uses for propylene glycol. It's used as an antifreeze, especially where a less-toxic alternative to ethylene glycol is desired, for de-icing aircraft, as a solvent for food coloring, as a moisturizer in hand sanitizer gel, hand cream, and cosmetics, and to provide a pleasing texture to baby wipes. It is found in wallpaper stripper, adhesives, pipe tobacco and tire sealant. Being colorless and close to odorless, propylene glycol has made an ideal additive contributing slickness, moisture and the property of staying liquid at a low temperature.

Controversy

Although propylene glycol is a common additive in many household and personal care products, it is not entirely harmless. In sufficient concentration and quantity, it irritates the skin and eyes. Skin Deep, the cosmetic safety database of the Environmental Working Group, lists scores of studies establishing effects including neurotoxicity, cancerous cell mutation, respiratory impact and more. Additionally, propylene glycol enhances skin absorption. Joanna Runciman of Actual Organics points out that although the ingredients in products such as shampoo have been tested separately, they have not been tested in combination. Propylene glycol might encourage the absorption of other chemicals, or chemical combinations, that may be harmful to the body.

References

• Environmental Working Group's Skin Deep Cosmetic Safety Database: Propylene Glycol
• Actual Organics: How to Avoid Toxins in Skin Care Products
• Natural-Health-Information-Centre.com: Propylene Glycol
• Environmental Working Group's Skin Deep Cosmetic Safety Database: Shampoos Containing Propylene Glycol
• Science Toys: Ingredients: Shampoo