Read the Label: Dimethicone

Photo: Graeme Montgomery/Trunk Archive

You don’t even realize how many personal care and beauty products you use everyday, from that glob of toothpaste in the morning to makeup wipes to clean the day’s grime off at night. With these little rituals, we’re putting hundreds of different chemicals onto and into our bodies daily. Shouldn’t you know what some of those things are? In this column, we chat with cosmetic chemist Randy Schueller (co-founder of The Beauty Brains), doctors, and other experts to dive deep into the ingredient lists of your favorite products.

Name: Dimethicone

Otherwise known as: Polydimethylsiloxane and Dimethylpolysiloxane—it’s sometimes confused with other ingredients in the silicone family (they have similar names like amodimethicone, PEG-12 dimethicone, and dimethicone copolyol), but those are water soluble versions with different properties.

What it does:  Dimethicone is a silicone-based oil. (More traditional oils from animal, vegetable, or mineral sources are carbon-based, says Schueller.) Dimethicone has the ability to repel water, which is why manufacturers use it as a moisturizing agent for both hair and skin. “On hair, it forms a thin reflective film that smooths the cuticle, makes hair easier to comb, and increases shine,” Schueller says.  “On skin, it prevents moisture from evaporating, thereby increasing the water content of skin. It can also act as a barrier to protect skin from damage.”

Related: Read the Label: Parabens

Where you’ll find it: Dimethicone is used in shampoos, conditioners, shine sprays, and some styling products. It’s also found in hand and body lotions, face creams, makeup primers, lipsticks and glosses, antiperspirant/deodorants, and shaving products.

Safety profile: The Cosmetic Ingredient Review Board (CIR) has determined that dimethicone is safe for use in cosmetics and personal care products. It’s also approved for use in Europe according to the Cosmetics Directive of the European Union. Because it’s so effective as a skin protectant, the FDA’s approved it as an over the counter drug for this use.

There are some reports of allergic reactions to dimethicone, though it’s hard to isolate an allergy since it’s so ubiquitous and products contain so many other chemicals and ingredients. Finally, dimethicone may contain traces of cyclotetrasiloxane and cyclopentasiloxane, other silicones suspected of causing health and environmental effects. “The residual amount is so small, though, that no harmful effects have been attributed to it,” Schueller says. (Dimethicone is not biodegradable, but it is absorbed by waste water treatment facilities.)

Related: Read the Label: Sulfates

Side effects: Silicone can build up on hair and ultimately weigh it down.

Alternatives: Water soluble silicones like dimethicone copolyol or traditional hydrocarbon oils such as mineral oil or vegetable oils may be used in place of dimethicone, though they don’t provide the same degree of occlusivity.