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I’m a fan of silicones. Even though I’m prone to psoriasis and the occasional acne on my forehead – I’m middle-aged now, but acne’s against against age discrimination- I have never encountered any issues with them. The word “silicones” is a generic term: there are hundreds of silicones with various properties. For this post, I researched the mother of all silicones: Dimethicone.
If you’re not a fan of Dimethicone because you read on Instagram that it is bad for the skin, I’m going to ask you a simple question: Do the influencers who say that provide any credible sources to back up their claims? Like links to relevant studies? Probably not!
2. What is Dimethicone?
Dimethicone is one of the most common silicones in skincare, haircare and make-up products. Also known as Polydimethylsiloxane, it is a multi-purpose compound that exists in a very wide range of viscosities. Very low molecular weight Dimethicone is as thin as water. Very high molecular Dimethicone has the consistency of silly putty!
Silicon Dioxide is a naturally occurring compound: it’s the major constituent of sand in many parts of the world as well in various gemstones, such as amethyst. However, the process of synthesizing Dimethicone from Silicon Dioxide is very complex and it can’t be considered a natural ingredient.
Fans of natural skincare would not be very happy if they read how it’s manufactured.
This doesn’t mean that Dimethicone is unsafe for the skin. Quite the opposite. There’s barely any research indicating that it causes side-effects.
3. Dimethicone in skin and hair care
Dimethicone is often combined with other silicones in skin care products. It is popular among cosmetic chemists for a variety of reasons:
- It improves spreadability of skin care products.
- It has a pleasant skin feel that is often described as “smooth” and “velvety”. It is often used in moisturizers. It is not particularly moisturizing on its own, though.
- It is used as a skin protectant.
- It is often found in make-up primers.
- It is used in some silicone gels for treatment of scars.
- It is used as a suspending agent in some serums, usually together with other silicones. When the serum is applied to the skin, the actives are absorbed while Dimethicone remains on the surface.
- It is often found in shampoos and conditioners to soften and detangle hair.
- It is an excellent remedy against lice.
Ok, this last property of DImethicone is not exactly related to skin care but I had to include it! I was very surprised when I read about it. 100% Dimethicone is very effective against lice and possibly safer than traditional medications.
4. Safety of Dimethicone
4.1. Is Dimethicone bad for skin?
It is often said that Dimethicone is comedogenic, irritating and drying. But there’s almost zero evidence from research that it’s any of those things.
Dimethicone is a well-researched compound and it poses a very small risk of adverse effects, even at a 100% concentration. One would expect that Dimethicone’s bad reputation would be justified by research to some extent. But that’s not the case.
Sometimes, where there’s smoke, there’s no fire. It’s just a smoke machine.
4.2. CIR verdict on Dimethicone
The CIR (Cosmetic Ingredient Review) Panel has reviewed many studies on the safety of Dimethicone. It concluded that it is a safe, non-toxic ingredient in cosmetics. Evidence from research on both humans and animals has shown that Dimethicone is very unlikely to cause irritation or allergic reactions.
In the same report, the CIR also reviewed some other other related silicones, such as Cetyl Dimethicone, Vinyl Dimethicone, Amodimethicone, Stearamidopropyl Dimethicone, C30-45 Alkyl Dimethicone and Stearyl Dimethicone. These were also found to be safe.
4.3. Dimethicone and Atopic Dermatitis
A study on samples of human skin tissue showed that Dimethicone does not disturb the skin barrier. This means that Dimethicone is safe for conditions with an impaired skin barrier, such as Atopic Dermatitis.
A lotion consisting mainly of Dimethicone and Squalane was found very effective against lice. It was well-tolerated by children over 12 months with atopic skin.
The lotion contained Dimethicone of various molecular weights. This means that various forms of Dimethicone are safe for atopic skin.
By the way, there’s recent evidence that cyclic silicones, such as Cyclopentasiloxane, may have a negative effect on the skin barrier. But, so far, there’s no such evidence for Dimethicone.
4.4. Potential impurities in Dimethicone
Researchers point out that high molecular Dimethicone needs to be properly purified. Interestingly, the potential impurities are mainly other low molecular weight silicones or low molecular weight Dimethicone!
Do I sound outrageously geeky for thinking this is interesting!?
For example, Dimethicone might contain residual Cyclopentasiloxane. That’s not a big deal, since the latter is also very common in cosmetics. Still, it’s a different silicone with its own distinct properties. A product that contains Dimethicone and Cyclopentasiloxane is not exactly the same as a product that contains pure Dimethicone.
And obviously it’s only fair for consumers to know exactly what they put to their skin. But I honestly doubt that a tiny amount of these impurities will make a difference on your skin. And I’m pretty sure that reputable ingredient suppliers take all the necessary steps to eliminate them.
Medical Grade Silicones, however, must be purified to meet certain standards.
5. Dimethicone, molecular weight and volatility
What are volatile substances?
Simply put, volatile substances evaporate rapidly from the skin.
Essential oils and rubbing alcohol, for example, are volatile. Same goes for some other silicones, such as Cyclopentasiloxane. On the other hand, vegetable oils are non-volatile.
According to some websites, Dimethicone is a non volatile silicone but this is not true. Dimethicone can be volatile too.
Dimethicone’s volatility and consistency depend on its molecular weight. Very low molecular weight Dimethicone is a thin liquid and it evaporates from skin. It leaves a lightweight, dry finish.
As its molecular weight increases, Dimethicone becomes less volatile and thicker.
Dimethicone of a high molecular weight is very thick and non volatile: it stays on the skin. It may feel heavier and greasier.
However, Dimethicone is usually only one of the ingredients in your skin care products. So, whether a product will have a dry finish on your skin or not, depends on the whole formula, not just Dimethicone.
6. Moisturizing properties of Dimethicone
Dimethicone is essentially non irritating but it’s not very moisturizing.
How occlusive is Dimethicone?
It is often said that Dimethicone moisturizes by forming a protective barrier that prevents water loss from skin. Compounds that do that are called occlusives.
Some websites go as far as saying that Dimethicone is so occlusive that it suffocates skin. Nothing could be further from the truth.
In reality, Dimethicone is not occlusive: a report by a silicone manufacturer describes most silicones as non-occlusive! Some silicones are more occlusive than others, but Dimethicone is essentially non-occlusive. When Dimethicone dries on your skin, it forms a permeable film that allows water to evaporate.
Dimethicone is not particularly moisturizing
Dimethicone is not a great moisturizer for skin, exactly because it is non-occlusive: it doesn’t do a great job of retaining moisture. Petrolatum is way better at that. It creates a barrier that holds moisture for hours.
The largest silicone manufacturer actually mentions that silicones are not moisturizers. Because of their silky finish, they feel moisturizing and refreshing, even if they don’t moisturize.
I sense that non volatile Dimethicone will slow down moisture loss a bit, but that may not be enough for dry skin.
My issue here is that Dimethicone may give a false sense of hydration. That could be a problem if you have dry skin and you use products that don’t contain other moisturizing ingredients.
Fortunately, most moisturizers typically have a variety of occlusive, emollient and/or humectant ingredients. Dimethicone may slow down transepidermal water loss to a small degree and my guess is that it works synergistically with ingredients such as Glycerin, Petrolatum and Shea Butter.
In one study, the combination of Dimethicone with Glycerin did have a moisturizing effect.
7. Does Dimethicone not allow skin to breathe?
You may have read on various websites that silicones form a rubber-like film that suffocates skin, trapping bacteria and dirt underneath. These websites typically recommend using natural oils instead of silicone-based products.
A), hopefully you don’t apply your skincare products right after rolling in the mud.
B), now all I can think of is that rolling in the mud would be a great way to let off steam.
And C), oils are semi-occlusive and they form a barrier on the skin. Oils are way more occlusive than Dimethicone and most silicones! This means that oils will trap more dirt than Dimethicone! If your skin is already dirty, I guess.
8. Dimethicone as a skin protectant
Skin protectants products are meant to protect skin from irritants and allergens. They’re ideal both for chronic atopic dermatitis and the occasional irritation.
In the US, the use of “skin protectant” is regulated by the FDA: products containing 1-30% Dimethicone can be listed as skin protectants.
I think that Dimethicone may not be a great skin protectant on its own, since it’s not occlusive.
However, combined with other ingredients, it does seem to form a protective barrier on the skin: a barrier cream containing Dimethicone was shown to protect skin from parasites that cause Schistosomiasis. This is the second most prevalent disease in Africa. Thanks, Dimethicone!
Products with Dimethicone may also protect skin from irritants at home or at work, such as ingredients in household cleaning products.
My guess is that non-volatile Dimethicone will work best as a skin protectant since it doesn’t evaporate from skin.
9. Does Dimethicone cause acne?
Dimethicone is considered non-comedogenic and non-acnegenic. Dimethicone is rather common in acne moisturizers, often combined with Glycerin. It may slow down TEWL (transepidermal water loss) a bit without a greasy feel.
The combination of Glycerin and Dimethicone may even soothe the irritation from acne medications, such as Benzoyl Peroxide, Clindamycin and Tretinoin.
I personally believe that anecdotal evidence matters too. Many Reddit users have mentioned that products with Dimethicone worsened their acne.
But unfortunately, it’s difficult to establish if it was Dimethicone that caused the issue in personal experiences like these. I think that many users put the blame on Dimethicone and other silicones because of their bad reputation.
But in many cases, it could be another, less suspicious ingredient causing the problem.
Or the issue might be caused by layering various skincare products with sunscreen and make-up on top. And layering loads of products is super common nowadays.
However, I wouldn’t entirely dismiss the possibility of Dimethicone clogging pores in a small number of individuals. But I think that it is way less common than we think.
I think that there are two main reasons behind the backlash against Dimethicone and other silicones.
Brian Barron from the Paula’s Choice brand believes that the backlash may have originated from the mistaken belief that silicones cause acne. As I mentioned above, Dimethicone is not likely to clog pores. However, many acne-sufferers think it does. And that was already the case when I got into skin care in 2006.
Michelle from Labmuffin thinks that humans have a tendency to believe that natural means better and safer. All-natural, undiluted Olive oil is way more likely to irritate skin and exacerbate dandruff than Dimethicone, but many influencers think otherwise!
My skin care odyssey started in 2006 and sometimes I’ve experienced irritation from skin care products. On a few occasions, I put the blame on Silicone. But I was in denial, really: It was frequent (ab)use of Retinol, L-ascorbic acid or Glycolic acid. All of them are great ingredients, but some people can’t use them daily or they just can’t use them at all.
So to cut an epically long story short, give Dimethicone a chance!
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What’s your experience with Dimethicone? Leave a comment below!