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Do you want to make sure you are using toxic-free makeup and skin care products? So do I. One of the most controversial ingredients I have seen in my career as a consumer product researcher and product manufacturer advisor for ingredient safety is dimethicone. In fact, I have been researching it for years now because there is a lot of negative information about it on the Internet. For example, some say that it causes acne because it coats the skin and prevents it from breathing. Others even say that it causes endocrine disruption, reproductive toxicity, and cancer. By the way, I highly recommend asking those bloggers for sources of their information, which do not include links to other bloggers. In this post, you will learn my findings about dimethicone safety so you can make informed and practical decisions.
How I do research
To begin with, I formulate my opinions by reading scientific studies on the subject and do not just rely on hear-say. I believe it is important to pass along only accurate information, so I turn to scientific and medical sources. Therefore, when you hear scary claims about a product or an ingredient, I encourage you to ask for the sources of their information.
I say this because a lot of bloggers simply repeat what they read on the Internet. There is a lot of misinformation out there! Once something is written, it can take on a life of its own. But before I publish something, I always do my best to track down the original sources of information, so I am not simply repeating something that may not be true. It takes a lot more time to do things this way, but it is my obsession to find the truth.
Here is what I have learned about this widely used ingredient.
What is dimethicone?
First, its chemical name is polydimethylsiloxane (PDMS), and it is also known as linear silicone based polymer (source). The key word here is linear. Perhaps there is negative information about dimethicone due to confusing it with cyclic silicones such as cyclopentasiloxane (D5) or cyclotetrasiloxane (D4). But cyclic and linear silicones are different. Yes, I know that they share “-siloxane” in their names but that does not mean they share negative health side effects. And I can say that with confidence because both linear and cyclic silicones are well-studied. You can learn more about the safety of cyclic silicones in my blog titled The Intriguing Story Of Cyclopentasiloxane.
Second, to avoid confusing dimethicone with cyclic silicones, please know that dimethicone can be identified (like any ingredients listed in products) and therefore distinguished from cyclic silicones with CAS Registry numbers, unique identification numbers assigned by the Chemical Abstracts Service. Per the 2003 Cosmetic Ingredient Review (CIR) Expert Panel report, it has 3 CAS numbers: 9006-65-9, 63148-62-9, and 9016-00-6.
Third, dimethicone is a well-studied ingredient so you can look it up in a number of different scientific, medical, and regulatory agencies, which I have done. And I did not find any negative health impact information in the US, European, or Canadian agency databases. Please read further for details on that.
For example, the Cosmetic Ingredient Review (CIR) Panel reviewed dimethicone safety for use in cosmetics. As a result, the panel compiled all available data on dimethicone from over 100 independent studies. Although I do not take the panel’s conclusions as the last word on safety, their assessments are helpful, if only to provide some context.
Before we dive into the details, let’s talk for a second about an opinion the Environmental Working Group (EWG) expresses about dimethicone in its Skin Deep database. At first, the EWG rated it 3, then 1-3, and now it is 2-4. If you scroll down the page, you will see that their main source of negative information is the Environment Canada Domestic Substance List (DSL), an inventory of both safe and harmful chemicals. To verify the accuracy of their information, I accessed the dimethicone listing on the DSL here. As you can see, dimethicone is indeed listed, which means that the manufacture or import of this substance does not trigger notification to the Canadian government. However, just because it appears on the DSL does not mean it is harmful. It just means that the Canadian Government is aware of its existence. In other words, I was unable to verify the EWG sources of negative environmental and health impact. Also, know that the EWG accepts and approves products with this popular ingredient in their paid EWG Verified program. To learn what else to keep in mind when using the EWG Skin Deep database, read my post Use Skin Deep Database the Right Way.
Is dimethicone bad for skin?
First of all, in skin irritability tests that the CIR refers to in its report, the scientist used this ingredient in an undiluted form. In contrast, this would never happen with skin sensitizers such as formaldehyde-releasing preservatives. But despite its undiluted form, the scientists did not find it to be an allergen in animal studies. Also, after tests on 83 humans at 5% concentration, no skin reactions occurred.
Moreover, I found two studies (you can access them here and here) that talk about its effectiveness in the treatment of hand contact dermatitis and prevention of contact dermatitis caused by Sodium Lauryl Sulfate (SLS).
Does it cause any health problems?
For starters, I have read a comprehensive write up on dimethicone safety in Ullmann’s Encyclopedia of Industrial Chemistry. The publication points out that it is a well-researched substance because of its broad applications. Thus, the 708-page manuscript states that it showed no health effects, even when scientists administered it orally in big doses.
Next, the CIR Expert Panel reports that the skin does not absorb dimethicone because of its large molecular weight.
Furthermore, Canada Health does not list dimethicone on either their Prohibited or Restricted Cosmetic Ingredient lists.
Further, the European Commission did not place any bans or restriction on this popular ingredient.
In addition, the European Union Chemicals Agency database reports neither negative health effects or environmental impact. On the other hand, there is some limited evidence that the small particles of dimethicone can be harmful to our lungs when inhaled in big quantities. Although the CIR Panel does not believe that the particle used in cosmetic products are small enough to impact our lungs negatively, to be on the safe side, I do not recommend this ingredient in spraying products
Is dimethicone a carcinogen?
According to the CIR report, there are no links to cancer even when animals ate this ingredient in big doses.
Next, the California Proposition 65 list, which contains a wide range of naturally occurring and synthetic chemicals that are known to cause cancer or birth defects or other reproductive harm. The Prop 65 list does not include PDMS. To be sure, I used all three CAS numbers to search for it on the list.
Additionally, the World Health Organization reports the lack of carcinogenicity evidence in long-term feeding studies in rats at alternating doses up to 1500 mg/kg per day or up to 1875 mg/kg per day (source).
Finally, dimethicone is not on any lists of known and probable human carcinogens (source).
Does Dimethicone cause acne?
Apparently, there are claims on the Internet that it creates an unbreathable barrier on the skin, which may make the skin dry and even cause acne. I have not found any scientific information to that effect. However, based on my experience as a product formulator advisor, I have two things to say about that.
Yes, it is true that this ingredient creates a barrier on the skin, which means it reduces loss of moisture by trapping it. But to trap moisture, you must have it, to begin with. So, if you put it on dry skin, you won’t have anything to trap. Therefore, if you use a skin protectant with this ingredient, be sure to apply it on damp skin.
In addition, this moisture trapping ingredient is often used in hair products such as shampoos or conditioners as a hair moisturizer. It is not recommended for curly hair as it can weigh down the hair and flatten curls. Personally, I do not use any shampoos or conditioner that contain dimethicone. (My favorites are Pure Haven Supergreens.)
As for acne, there are different types of acne and different products use different concentrations of this popular ingredient. It is probably possible to make your acne condition worse if you use a skin protectant with high amounts of dimethicone when it is listed as one of the first ingredients. But here is the thing – try it and see for yourself.
Personally, I have experience using only some makeup products that contain dimethicone. For example, I have been using Crunchi Beautifully Flawless Foundation (learn more about it here) and Beautycounter Twin Skin Featherweight Foundation (learn more about it here) and have not had any acne problems. By the way, Crunchi foundation contains a very tiny amount of dimethicone; therefore it is listed last on the list of ingredients.
As a makeup researcher since 2013, I believe that a well-performing makeup without some types of silicones do not exist. You need them to help makeup products to spread evenly, conceal wrinkles, and in some cases create a dewy effect.
Is dimethicone an endocrine disruptor?
Again, per multiple studies described in the CIR report, there are no links to endocrine disruption. And I have not found any medical studies outside of the report to link dimethicone to hormone disruption.
In addition, the World Health Organization (WHO) allows its use in food as an anticaking and antifoaming agent (source). It does not mean, though, that I recommend eating food with it or any other processed food. It simply means that it is considered a food-grade ingredient by the International scientific community.
In some literature, there is mention that in mammals, certain phenylmethyl-substituted siloxanes are linked to endocrine disruption. However, as I described earlier, phenylmethyl-substituted siloxanes can be of two types: linear and cyclic. And only cyclic ones, which does not include dimethicone, are linked to endocrine disruption in animals. You can learn more on that in the blog titled, The Intriguing Story Of Cyclopentasiloxane.
Further, you might find the Food and Drug Administration (FDA) article about “forever“ Per- and polyfluoroalkyl substances (PFAS) in cosmetics, which lists perfluorononyl dimethicone as one of the PFAS ingredients in cosmetics. Yes, please be sure to avoid it but know that dimethicone and perfluorononyl dimethicone are two different substances. The emphasis is on perfluorononyl, that’s the PFAS component of this polymer.
Is dimethicone toxic for the environment?
Obviously, I was concerned about the effects of this widely used ingredient on the environment.
For instance, Ullmann’s Encyclopedia of Industrial Chemistry explains that it is mostly non-biodegradable but is not harmful to aquatic life (plankton, crustacea, mussels, fish). Even silicone fluid administered with food showed no effect on fish. Also, the symbiosis of microorganisms such as bacteria and algae has not been disturbed by this ingredient dissolved in water. The European Union Chemicals Agency database also cites no ill effects on aquatic life, confirming dimethicone is safe for the environment.
While it is non-biodegradable, it is eliminated from sewage water because it is absorbed by sewage sludge. The reason it ends up in the oceans is that sewage sludge is often dumped into the oceans.
Are polydimethylsiloxanes safe for the environment?
Dimethicone belongs to the group of chemicals called Polydimethylsiloxanes. There are reports that they exhibited toxic effects in fish. However, the polydimethylsiloxanes at issue were emulsifiers and were at concentrations up to 10,000 ppm. So, it is not believed that dimethicone as used in cosmetics is harmful to the environment.
And the good news is that polydimethylsiloxanes are non-bioaccumulative. This means that as soon as the fish were transferred out of the environment with polydimethylsiloxanes, they were rapidly eliminated from the fish tissue.
In addition, polydimethylsiloxanes can be degraded and absorbed by the environment if a non-biological step is taken initially such as burning. You can read more about that here.
What are other forms of silicone?
In addition to dimethicone, there are other types of silicone, such as phenyl trimethicone, cyclopentasiloxane, and PEG-10 dimethicone.
Is phenyl trimethicone safe?
This white silicone fluid is highly water resistant and by trapping water in skin or hair, it adds flexibility. So, it works as a hair and skin-conditioning agent, and an antifoaming agent. Thus, the EWG Skin Deep database rates it 1 out of 10 (with 10 as most toxic) but indicates only limited safety data. “Limited safety data” is an acknowledgement that although the substance apparently is not dangerous – garnering an EWG rating of “1,” it may seem non-toxic because scientists haven’t studied it enough.
Furthermore, the Cosmetic Ingredient Review (CIR) Expert Panel considers phenyl trimethicone safe for use in cosmetics and personal care products. In fact, the panel reviewed acute oral data showing that the ingredient was relatively non-toxic. Additionally, it reviewed acute and subchronic dermal studies that also showed its non-toxic nature.
Specifically, phenyl trimethicone is nonmutagenic, nonirritating to the skin and eyes, and is not a sensitizer to humans. Note also that the tested doses were larger than the concentrations used in cosmetics and personal care products. This fact should provide even more peace of mind. Moreover, because the UV spectrum indicated only weak absorbance at 327 nm, the panel concluded that it is not a phototoxicant or a photosensitizer (source).
Finally, just as in the case with dimethicone safety, the European Chemicals Agency has classified no hazards based on the notifications submitted by companies. As a result, the general provisions of the Cosmetic Regulation of the European Union allow the use of phenyl trimethicone in cosmetics and personal care products marketed in Europe.
Is cyclopentasiloxane safe?
Unlike dimethicone, cyclopentasiloxane raises some concerns, in my opinion. You can read more about this ingredient in my post about cyclopentasiloxane safety. My personal recommendation is to reduce your usage of products made with it. For instance, one of such products is Old Spice antiperspirant & deodorant.
Is PEG-10 dimethicone toxic?
To begin with, PEG-10 dimethicone is a synthetic polymer that consists of PEG (polyethylene glycol) and dimethicone. Due to the presence of PEG, it is an ethoxylated ingredient made through the process of ethoxylation. As a result, it may contain potentially toxic manufacturing impurities such as carcinogenic 1,4-dioxane. To find out how to identify all ethoxylated ingredients, read my post Hidden Ingredients in Cosmetics blog.
Therefore, I do not recommend products with ethoxylated ingredients. Namely, beware of such ingredients as PEGs, polysorbates, and those whose names end with “-eth” (e.g., Laureth). For example, Bare Minerals foundation uses PEG-10 dimethicone in their formulation. To read about a safe liquid foundation with dimethicone, visit my post The Non-Toxic Foundation that Works So Well.
Conclusion about dimethicone safety in toxin-free makeup
To sum up, I have not found any evidence that this cosmetic ingredient is toxic when applied on the skin. It is one of the well-studied ingredients, and scientists have not found anything wrong with it. Thus, I believe it is safe for humans when used in makeup, skin care, and hair care products. Based on my thorough research, I do not think it can increase the risks of allergic contact dermatitis, allergic reactions, skin irritation, cancer, or endocrine disruption.
In addition, I believe that dimethicone in makeup is necessary to improve its performance. However, you can easily avoid it in haircare or skincare products, if you want to.
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