Silicones are among the latest ingredients clients love to hate. From health concerns to worries about environmental safety, silicones have been hung with a black shroud since the early 1990s when breast implants were first connected to women’s health issues. Since that time, silicone technology has been expanded, making this family of chemicals among the most used in the modern world. Even so, this doesn’t mean silicones are safe. So here are some facts and a little basic chemistry to help clear up the mythology now being spun about silicones.
Myth No. 1: “Silicone” is the name of an ingredient.
Silicones are a family of chemicals known as a class. No ingredient on its own is named “silicone,” which means you should never see silicone in the ingredient list of a product. Chemical classes share common traits. In this case, silicones are a class of polymers—molecules made of one or more (poly) repeating units (mers), usually put together in a straight line like the vertebrae that form your spine. In the case of silicones, units are made of two basic elements linked together: silicon and oxygen. This is written chemically as SiO. When they’re linked together to form a silicone, the SiO polymer is the backbone onto which other molecules can be attached, allowing for a variety of applications, functions, textures and benefits.
Due to the enormous variety of compounds that can be developed from silicones, they are among the most used family of materials in the world. You’ll find them in pharmaceuticals; medical supplies and equipment; automotive; aviation; astronomy; foods; beverages; biotech; construction; appliances; plumbing; paints; textiles; and toys. From 2006–2008, more than 6,000 patents were granted in the United States for innovative, never-before-seen silicones for use in cosmetics.1 These new silicones make serums silkier; give lotions and skin a satin and flawless finish; make BB and CC creams possible; minimize pores and wrinkles; reduce or eliminate irritation from sunscreens; and act as launchpads from which key performance ingredients can penetrate the skin. All in all, silicones have added new dimensions to skin care that make products more effective and more fun to use.
Myth No. 2: Silicones are harming the ozone layer.
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Chloroflurocarbons (CFCs) are the chemicals harming the ozone layer, not silicones. Chlorine gas disrupts ozone formation in the Earth’s upper atmosphere, which is often described as harming the ozone layer. Silicones do not contain chlorine, which means they can’t contribute to this disruption.
Myth No. 3: Silicones in cosmetics cause rheumatoid arthritis, lupus, scleroderma, chronic fatigue and cancer.
Applied topically, as they are in skin care, silicones are too large to penetrate the skin, so they cannot cause or worsen these conditions. However, concerns about silicone safety did not come from their use in cosmetics, pharmaceuticals or even wound care, where there is no skin to act as a barrier. They arose from silicone gel-filled breast implants. In fact, these concerns underlay the U.S. Food and Drug Administration’s (FDA) 1992 decision to place a moratorium on silicone gel breast implants due to inadequate safety and effectiveness data from the implant manufacturers. Later that decade, the FDA again allowed silicone gel-filled breast implants, but only for reconstruction and revision patients. It wasn’t until 2006, after years of safety studies, that the FDA completely lifted the moratorium, and silicone gel-filled breast implants again became available for everyone.
Myth No. 4: Silicones are not biodegradable.
Although silicones aren’t biodegradable in the traditional sense, they do degrade in the environment, where they break down into water, silicic acid and carbon dioxide. The degradation trigger for low molecular-weight silicones, such as cyclopentasiloxane, is sunlight and oxygen, but heavier weight silicones aren’t susceptible to UV, oxidation or ozone for that matter. They adsorb to sludge in wastewater treatment plants, where they are incinerated, entombed in landfills, or spread on golf courses, woodlands and agricultural fields as fertilizer. When deposited over soil, mineral clays act as a catalyst to undo the silicone’s polymer backbone. This can take weeks to years if the soil remains wet, but if the soil dries, it can take only days. Testing of soil treated with high levels of silicones showed no soil microorganisms are harmed in this process nor is plant growth affected.2
Myth No. 5: Silicones cause irritation.
Silicones don’t irritate the skin. They actually lower or eliminate irritation because they cause ingredients to spread evenly during application, which prevents pocketing and minimizes percentages of potentially irritating forms of cosmetic and drug ingredients. These include alpha hydroxy acids (AHAs), salicylic acid, strong emulsifiers and surfactants, benzoyl peroxide and organic sunscreens, such as oxybenzone, avobenzone and octinoxate. Silicones are used safely on all forms of sensitive skin, including that resulting from acne, rosacea, eczema, psoriasis, post-surgery, burns, diaper rash and skin ulcers.
Myth No. 6: Silicones are allergens.
Silicones are too large to enter the skin, so they can’t trigger an allergic reaction because they can’t react with the immune system. In fact, they’re so biologically inert when in contact with the skin, silicones are now replacing latex, a common allergen in adhesives, gloves and a wide array of other items. Silicones are also used on open wounds because they shorten healing time and do not promote bacterial growth.
If you have clients who are convinced they are allergic to silicones, rather than avoid silicone-containing products, suggest an allergy test. Because silicones don’t cause skin allergies, a new world of care will open up to your clients when silicone allergy is disproven.
Myth No. 7: Silicones aren’t natural.
Silicone science starts with sand, also known as silica. Made of finely ground quartz rock, sand is composed of the two most abundant elements in and on the earth: oxygen and silicon. Together, they form roughly 25% of the Earth’s crust.1 Natural silicon-based materials have been part of human survival since the Stone Age: The stones that made up the key survival technologies from that era—including arrowheads, bowls and grinding stones—were formed from flint, granite, sandstone, volcanic rock or other silicon dioxide-based materials. Later, two other silicon dioxide technologies, glass and ceramics, improved mankind’s lot even more.
Many people get confused when it comes to the different terms used to describe silicones, so here’s a guide.
- Silicon. Fourteenth on the periodic table, this is the second most abundant element on earth and the key element in silicone chemistry.
- Silica. Made of silicon dioxide, silica exists in a fairly pure state in sand, which is the key source material for silicone production. When listed as a cosmetic ingredient, silica represents silicon dioxide, not silicone.
- Silicone. See myth No. 1.
Myth No. 8: Silicones contribute to smog.
The chemicals that contribute to smog are volatile organic compounds (VOCs). These include acetone, ethyl alcohol, isopropyl alcohol, methacrylates and ethyl acetate, found in fragrances, as well as nail and hair products. Because silicones are inorganic, they can’t possibly be VOCs, so they can’t contribute to smog formation.
Myth No. 9: Silicones make skin greasy.
If that’s the case, your client is using the wrong formula for her skin. Most silicones are invisible when they’re resting on the skin, and some actually absorb sebum and mattify the skin, visibly minimizing pores in the process.
Myth No. 10: Silicones suffocate the skin.
Silicones are breathable: They allow oxygen, nitrogen and water vapors to pass through them on the way to, or out of, the skin. However, most silicones do not allow water to penetrate, making them excellent at reducing transepidermal water loss (TEWL)—a leading cause of skin dryness and dehydration.
Myth No. 11: Silicones clog pores and cause breakouts.
Because they are unaffected by oxidation, silicones are noncomedogenic, do not go rancid and, because they are not irritating, they are nonacnegenic. They’re also hostile to bacterial or other microbial growth. However, they can increase the penetration of some ingredients, which, when the product includes common irritants, such as fragrance or pore-cloggers like lipid-rich plant oils, may be the actual culprits behind breakouts and blackheads.
Myth No. 12: Silicones bioaccumulate in humans and other animals.
Silicones do not bioaccumulate because they are too large to pass through cell membranes—a key requirement for bioaccumulation. Tests on organisms that dwell in water, soil or sediment have shown no adverse effects at concentrations well above those found in the environment2, nor are silicones metabolized by humans, other animals or microorganisms.
- Impermeable to the skin’s barrier and cell membranes;
- Environmentally degradable; and
- Hostile to microbial growth.
And that’s the bottom line on silicones in skin care.
1. AJ O’Lenick, Silicones for Personal Care, 2nd Edition, Allured Publishing Corp., Carol Stream, IL (2008)
2. G Chandra, The Handbook of Environmental Chemistry, Organosilicon Materials, Springer-Verlag, Berlin (1997)
Rebecca Gadberry is an independent product developer, educator and researcher with more than 40 years of experience in the fields of skin care and skin biology. She is also the lead instructor and course developer for the highly acclaimed Cosmetic Sciences program at the University of California, Los Angeles (UCLA) Extension and has developed more than 1,300 cosmetic products. Gadberry can be contacted at firstname.lastname@example.org.