Dimethicone, also known as polydimethylsiloxane (PDMS), is a silicone oil with distinctive properties that make it a useful ingredient in many skin and hair care products. It has many industrial applications as well, and is even an additive in some foods. People widely use products containing the compound, and generally report few adverse effects, although some individuals do have sensitivities to it.
Use in Personal Care Products
Products such as hair conditioners and shampoos frequently contain dimethicone to facilitate the combing of tangled hair, as well as to give hair a brighter shine. It forms a slick lubricating coat around each strand of hair so that a comb will move through the hair with less resistance. Likewise, it acts as a skin protectant and emollient, appearing as an ingredient in many over-the-counter moisturizing lotions and skin creams, as well as in some makeup products. Even diaper rash creams for babies often add this chemical to soothe the irritated skin.
Safety
The U.S. Food and Drug Administration (FDA) has approved adding PDMS to products such as those listed above, and decades of consumer use have shown it to be largely safe. One area that has raised concern is the use of the substance as a filling for breast implants. For years, PDMS silicone implants were the standard, but recent medical concerns have caused a gradual shift to implants filled with saline.
Expectant and breast-feeding mothers are advised to consult a physician before using any product that contains dimethicone. It is possible for a consumer to find out if dimethicone, or one of its variants, is present in a particular product by reviewing the list of ingredients. Names such as Amodimethicone, Stearoxy Dimethicone and Behenoxy Dimethicone indicate the use of polymers based on this manmade substance.
Side Effects
Some side effects have been reported from the use of PMDS products; they include mild itching and stinging or burning sensations. Allergic reactions such as hives, sudden respiratory problems, and swelling in any part of the mouth or face represent can also happen. Users of dimethicone creams may be surprised to find that the product can actually worsen dryness in some individuals. This is not necessarily a sign of ineffectiveness, but may instead indicate an allergic reaction that should not be ignored.
Should such symptoms appear, doctors recommend immediately discontinuing use of the product. Seeking medical attention is a good idea if the reaction becomes severe, or does not improve quickly. A pharmacist can be another good resource for guidance regarding side effects.
Other Uses
Dimethicone is widely used in non-cosmetic products as well. Because of its corrosion-inhibiting properties, it is a popular additive in industrial lubricants. Makers of processed foods use the compound to prevent caking and foaming. It is also the primary ingredient in the world-famous toy known as Silly Putty®.
Composition
Silicon dioxide, commonly referred to as silicon or silica, is a naturally occurring element in the earth. Chemists have successfully combined silica with oxygen, hydrogen, and carbon. These chemical compounds, which may also include additional elements, are known as silicone polymers, or simply silicones. A polymer is a large molecule that is composed of units of smaller molecules that are repeated in a molecular chain. Not all silicones are identical; they differ depending on how the manufacturer mixes and fuses the elements together. To avoid confusion, remember that "silicone" is a product derived from "silicon."
Physical Characteristics
PMDS is unusual in that it tends to share some of the properties of both a solid and a liquid. Chemists refer to this quality as viscoelastic. At room temperature, a solid mass of the material will at first feel and act very much like rubber. If left on a solid surface over several hours, however, it will eventually ooze outward to cover the whole area. A person can then peal it off to reveal a perfect mold of the object. This semi-solid state is partly what makes the substance so versatile.