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The Story of Cyclopentasiloxane Safety

Written by Irina Webb

Hair spray, sunscreen, antiperspirant, deodorant, mascara, foundation, decorative makeup – these are some of the products that use this ingredient.  It helps create that soft, silky, and moist feeling on your hair or skin.  But is it safe?  Today, you will hear the story of cyclopentasiloxane to be able to draw your own conclusion about its safety.  The use of cyclopentasiloxane in skin care and hair care products has caused some controversy.  So, read on to discover the truth about this ingredient and see my suggestions for safe skin care and makeup.

Cyclopentasiloxane - Safe or Toxic? A picture of the use of cyclopentasiloxane in skin care and hair care.

I meticulously study ingredients before recommending a product.  

When I do research on product ingredients – and I have been doing it since 2012 – I take a rounded approach. 

First, I read as much as I can about the whole industry whose product I am surveying right now.  Second, I scrutinize the manufacturing processes to learn more about contaminants and harmful byproducts that may result from these processes.  Then, I study the ingredients of a particular product by going directly to chemical databases and scientific literature. 

They include the Occupational Chemical Database, the TedEx List of Potential Endocrine Disruptors, the California Proposition 65 List, and PubMed.  I also use the EWG database, but you should know how to use the Skin Deep database the right way.  There are many other sources that I turn to, and you can see them here.

Next, I contact the manufacturers and ask them questions about their choices of ingredients and production processes.  Finally, I test the products on me and my family.  On my blog, I recommend only those products that meet my strict criteria. 

Sometimes, there is no agreement on an ingredient’s harm or safety.  That is why it is important to look at the research yourself to understand what causes the controversy.  And this is exactly what we are going to do to solve the mystery of cyclopentasiloxane in skin care.

What is cyclopentasiloxane?  It is a conditioning ingredient in hair and skin products.

To begin with, its full chemical name is decamethylcyclopentasiloxane and it is commonly known as D5.  It is responsible for a silky and slippery feel to the skin and hair (source).

Further, D5 is an odorless and colorless liquid.  Interestingly, they use it in the dry-cleaning process (source).

Some research finds cyclopentasiloxane (D5) safe in topical products.

First, the European Scientific Committee on Consumer Safety (SCCS) deems cyclopentasiloxane in skin care safe.  However, they emphasize potential damage to the lungs through D5 inhalation in aerosols such as hair and sun care sprays. 

Additionally, the SCCS voiced a concern that D5 may contain trace amounts of cyclotetrasiloxane (D4).  The problem with D4 is that the European Union classifies D4 as toxic to reproduction (source and source).  Hence, the SCCS underscores the importance of keeping the level of impurity of D4 as low as possible.

Second, the US Cosmetic Ingredient Review Expert Panel (CIR) considers cyclopentasiloxane safe in the present practices of use and concentration.  This assessment also embraces cyclomethicone, cyclotetrasiloxane (D4), cyclohexasiloxane (D6), and cycloheptasiloxane (D7).  The Panel lists no contamination concerns with cyclotetrasiloxane (D4) but confirms the concerns regarding D5 inhalation. 

Thus, the report describes a 2-year study of rats exposed to high levels of D5 through inhalation.  As a result, the researchers found malignant endometrial tumors in the animals.  Yet, in topical products, the CIR Expert Panel found D5 to be safe. 

As for carcinogenic effects, they occurred only after 12-months of exposure to high doses of D5 (source).  The Panel concluded that it would not be applicable to topical products, deeming cyclopentasiloxane in skin care safe.

Other research suggests that D5 may cause endocrine disruption.

For starters, the Skin Deep database rates cyclopentasiloxane 3 (with most toxic 10) indicating a low concern of endocrine disruption.  To be an endocrine disruptor, a chemical must get into the body.  Can D5 in topical skin care products absorb through the skin?

Well, this research studied in vitro and in vivo percutaneous absorption of D4 and D5.  According to the study, most of the applied D4 or D5 evaporated from the skin surface.  The absorbed quantities were less than 1.0% for D4 and only 0.2% for D5.  Further, about 60% and 30% of the absorbed D4 and D5 respectively reached systemic parts demonstrating a low tendency to pass through the skin into systemic compartments. 

Although these amounts may seem insignificant, the “dose makes the poison” paradigm does not always apply to hormone-disrupting substances.  In fact, endocrine disruptors have nonlinear dose-response relationships.  It means that a low dose may be even more potent than a higher dose.  Indeed, some birth control pills have as little as 20 mcg (micrograms) of estrogen.  It proves that it does not take much to make one infertile (source).   

For this reason, the European Consumer Organization considers cyclopentasiloxane in skin care a potential hormone disruptor.  In addition, the European Chemicals Agency proposed a restriction for the use of D5 in leave-on cosmetics.  As a result, cyclopentasiloxane is being evaluated for possible endocrine disruption.  Moreover, it will probably be prohibited or severely restricted before this evaluation takes place (source).

Environmental effects of D5 are controversial.

To begin, in 2008, Environment Canada and Health Canada recommended adding cyclopentasiloxane to the List of Toxic Substances.  The main argument was potential immediate or long-term harmful effects of D5 on the environment and biological diversity (source). 

In response, the Silicones Environmental, Health and Safety Center (SEHSC) requested an investigation into the nature and extent of the D5 danger.  As a result, the board of review for siloxane D5 reported that it was not harmful to the environment (source).

According to this study, after evaporating, only a negligible fraction of D5 is available to go down the drain. 

On the other hand, a 2016 Swiss report links cyclopentasiloxane to cytotoxicity in human intestinal cells.  Because it bioaccumulates in the food chain, it impacts human health.  It may also end up in drinking water because classical water treatment systems seem unable to remove it. (1)  (Learn how to choose the best water filter system for your water and what to do about uranium in water.)

Cyclopentasiloxane in skin care products and my recommendations

Which popular brands use D5 in their products? 

For instance, Old Spice antiperspirants list cyclopentasiloxane as one of their ingredients.  Read my review of Old Spice antiperspirants to find out why I do not recommend them.  

Then, you can see this chemical in Arbonne skin foundation.  It is listed second, right after water, which indicates a larger amount is used than that of other ingredients.  The Il Makiage foundation that is gaining popularity on Instagram, also spots it second after water.

Is there a way to avoid D5 and still use a good-quality product?  Yes, there is.

When it comes to foundations, my first recommendation is Crunchi non-toxic foundation that works so well.  I have been using it for years now, not only because I like its performance, but also because I can stand behind its every ingredient.  After researching Crunchi product ingredients thoroughly, I became a Crunchi direct sales advocate.  Indeed, if I made my own cosmetics, they would not differ from the Crunchi non-toxic makeup and skin care lines.  Therefore, if you are looking for ways to make a bit extra money, Crunchi can be the answer for you.  Plus, you can buy products for you or your family at a discount.  Let me know if you would like to learn more.

My next choice is Beautycounter.  Check out my Honest Beautycounter Review to see which Beautycounter products I recommend and why.  As for foundation, Beautycounter has a great number of shades.  So, if you do not find your shade with Crunchi, Beautycounter is the second-best option.

Conclusion about cyclopentasiloxane  

To sum up, cyclopentasiloxane in skin care has been causing some controversy.  On the one hand, scientists consider it safe for topical application and the environment.  On the other hand, it is suspected of endocrine disruption and polluting the food chain and sources of drinking water.  While US scientists do not seem to see any reasons for concern, European scientists are sounding the alarm. 

Ultimately, my concern with cyclopentasiloxane D5 is its potential as an endocrine disruptor.  This is a serious matter, as chemicals can affect hormones even in small doses.  Given all the confusion around D5, I do not see any necessity to use products with this ingredient.  Even more so that we have Crunchi and Beautycounter as safer options.  In other words, if a concern exists, why risk it when there are products without the concerning ingredient.

As usual, I invite you to visit my shop for safe and healthy products.  Also, book a consultation with me and/or join the Savvy Consumer Circle to get timely help with your non-toxic journey.

(1) Etteieb, et al., Combining Biological and Chemical Screenings to Assess Cytotoxicity of Emerging Contaminants in Discharges into Surface Water, Water, Air, Soil Pollution, Volume 227 (9) – Aug 24, 2016.

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