Dimethicone is a widely used ingredient in skin and hair care products and can be added to formulas to perform a number of roles. The versatile ingredient is sometimes called polydimethylsiloxane or PDMS. At room temperature, raw dimethicone is completely clear and has a rubbery texture. In its liquid form, dimethicone is very thick and similar in consistency to honey. Some clear skin and hair care products are made thicker with the addition of dimethicone.
One of the primary building blocks of dimethicone is silicon, an abundant chemical element that is found in soil. Silicon combines with other molecules to form long chains known as polymers, and dimethicone is the most commonly used of these polymers. Dimethicone is generally made in industrial settings by combining the substance dimethylchlorosilane with ordinary deionized water.
Silicon and its polymers were first added to skin care products in the 1950s. Initially, dimethicone was used almost solely as an emollient, an ingredient that softens the skin by filling in the tiny gaps that exist between the dry, dead cells on the surface of the complexion. Early products that contained dimethicone included moisturizers and hand and body lotions, and many modern formulas of these products still use dimethicone to make the skin tissue feel more supple and smoother. Dimethicone is also used as an emollient in hair conditioners to make the hair strands silkier.
By the 1980s, the benefits of dimethicone and other silicon polymers were more widely understood, and the use of these ingredients in skin and hair care products expanded dramatically as a result. One of the first of these new functions of dimethicone was skin protecting. Because of its thick, viscous nature, dimethicone makes an excellent barrier on the skin tissue and can be added to products meant to prevent chaffing, chapping, diaper rash and other forms of skin irritation caused by friction and exposure to moisture.
The ability of dimethicone to form a barrier on the skin tissue also makes it effective for use as an occlusive agent. Commonly used in moisturizers, occlusives prevent moisture found in the skin tissue from evaporating into the air. Since dimethicone is both an emollient and an occlusive, it is an incredibly popular ingredient in products used to combat dry skin and prevent its return. Moisturizers that contain dimethicone are often most effective when applied immediately after bathing or showering when the skin tissue is most susceptible to the drying effects of the air.
The occlusive and emollient properties of dimethicone make the ingredient common in products used to treat certain types of skin conditions that worsen when the tissue becomes dehydrated. Among these conditions are rosacea, eczema and psoriasis. For people suffering from one of these chronic skin care problems, doctors may recommend using a moisturizer that contains dimethicone several times per day or prescribe a medication that includes dimethicone along with its active ingredients.
Dimethicone has many minor properties that make it useful as an ingredient in skin and hair care products. When added to liquids, dimethicone's thick texture prevents solutions from forming bubbles. As an ingredient in shampoos and cleansers, dimethicone helps prevent the products from becoming foamy when their bottles are handled. Dimethicone is also occasionally added to sunscreens to make them resistant to water.
In foundation cosmetics, dimethicone makes the pigments contained in the formulas spread more evenly over the skin tissue, producing more natural results. When combined with other silicon polymers in foundations, dimethicone forms a very thin film on the complexion. This film protects the pigments found in the makeup, allowing the foundation to produce longer lasting results.
The U.S. Food and Drug Administration (FDA) has approved dimethicone for use as an active ingredient in over-the-counter medicines used to protect the skin, such as diaper creams. For use in other products, the FDA has classified dimethicone in its "Generally Regarded as Safe" category. Clinical studies have shown that dimethicone does not cause genetic mutations or pose a risk for cancer. In addition, the ingredient is not a common allergen, meaning that hypersensitivity reactions to dimethicone are rare. Most often, people who experience redness or itching from a product that contains dimethicone have developed symptoms due to another ingredient in the product's formula.