Cyclopentasiloxane (D5)

Safety Information

The Silicones Environmental, Health, and Safety Center (SEHSC) of the American Chemistry Council, which is committed to the responsible use of silicones, continues to evaluate the science behind silicone and siloxane materials through rigorous research programs, including computer modeling, laboratory testing, environmental monitoring and other approaches. 

Expert Panel for Cosmetic Ingredient Safety

The safety of the cyclomethicones (including D5) has been reviewed on several occasions by the Expert Panel for Cosmetic Ingredient Safety (Expert Panel). In 1991, the Expert Panel that cyclomethicone was safe in the present use practices. 

In 2009, the Expert Panel re-opened the report on cyclomethicones to consider new data and to include the individual chain-length compounds – cyclotetrasiloxane (D4), cyclopentasiloxane (D5), cyclohexasiloxane (D6) and cycloheptasiloxane (D7) – now identified as separate cosmetic ingredients. The Expert Panel again  that the reviewed cyclomethicone ingredients are safe under current use practices.

The EU’s Scientific Committee on Consumer Safety (SCCS) reviewed the safety of cyclopentasiloxane (D5) in 2010, concluding that it does not pose a risk to human health when used in cosmetics products. However, SCCS noted that D4, a potential residual starting material in the manufacture of D5, is classified in Europe as toxic to reproduction. For this reason, cosmetics and personal care products manufacturers closely monitor and control the residual levels of D4. 

In a second review of cyclopentasiloxane (D5) safety in 2015, the SCCS noted that the level of D4 as an impurity in D5 should be as low as possible and the level of purity of D5 in cosmetics products put on the market should be > 99%.

In 2018, the European Chemicals Agency’s (ECHA) Member State Committee concluded that D5 met the criteria for a very persistent, bioaccumulative (vPvB) substance in the environment. And when it contains residual D4 at or above 0.1 %, it meets the criteria for a persistent, bioaccumulative and toxic (PBT) substance under REACH legislation (the Registration, Evaluation, Authorization and Restriction of Chemicals). 

Based on these findings, the European Commission amended Annex XVII to REACH, indicating that D5 shall not be placed on the market in wash-off cosmetics products in a concentration at or above 0.1 % after Jan. 31, 2020. Since those substances must be present in wash-off cosmetics products in a much higher concentration to perform their intended function, the concentration limit set by this restriction effectively ensures that all intentional use of D4 and D5 in the EU will cease.

In 2006, the Canadian government announced its comprehensive strategy for managing chemicals – the Chemicals Management Plan – to gather information on approximately 4,000 of the roughly 23,000 materials in commerce in Canada. These substances were categorized for further assessment to determine potential risks to health or the environment. Including D4, D5 and D6 in the program did not indicate a potential risk but allowed the Canadian government to gather information that would help provide a complete understanding of the human health and environmental effects of several cyclomethicone materials. 

An analysis of all safety studies and data on exposure through use of cosmetics products showed that none of these substances present a risk to human health as currently used. After reviewing information on bioaccumulation of these siloxanes, the government of Canada concluded that D5 is not harmful to human health or the environment.

Cyclopentasiloxane (D5)

What Is It?

Cyclopentasiloxane is a cyclic dimethyl polysiloxane commonly known as D5. Cyclopentasiloxane is a member of the family of ingredients which also include cyclotetrasiloxane (D4), cyclohexasiloxane (D6), and cyclomethicone, which is a mixture of the individual chain-length cyclic dimethyl polysiloxane compounds from D4 to D6.

Why Is It Used?

Cyclopentasiloxane is used in cosmetics and personal care products for its excellent skin conditioning and hair conditioning properties. It is also used as a solvent when rapid evaporation of the solvent is desired, in products like deodorants and antiperspirants that coat the skin but do not remain tacky after application. 

Cyclopentasiloxane also facilitates a smooth texture and an even application in products, including sunscreens, shampoos, conditioners, moisturizers, lotions, etc.  

Scientific Facts

The cyclomethicone family of ingredients creates many positive qualities associated with personal care products: luxuriant texture, silky smoothness, luster and smooth applications. These ingredients help make personal care products non-stinging and non-irritating. For example, cyclomethicones reduce the white residue and tacky feel of antiperspirants in deodorants and help “long-lasting” makeup retain its color and luster. With cyclomethicones, shampoos and conditioners shine better, and sunscreen products obtain stronger SPF. They also provide smooth and even application of makeup, lotions, sunscreens and cleansers.