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Dimethicone Debate

Dimethicone: What does this word mean? Some easily impressible journalists and bloggers seem to think that it’s something really terrible that should not ever be used in cosmetic skincare.

Let’s look into it, shall we. 

Dimethicone’s chemical name sounds rather intimidating—Polydimethylsiloxane (PDMS). It is a polymer—a substance that consists of many identical molecules. Polymers are not necessarily synthesised—they can be organic too, and a lot of them are present in the human body, hyaluronic acid being one of them. Maple syrup and cane sugar are made up by polymers as well.

So, we’ve established that dimethicone is a polymer. It is made up by a large number of molecules, all identical and based on silicone [O-Si(CH3)2]n.

This makes dimethicone basically an organic silicone. It is an optically clear, inert and scentless silicone oil. So what makes dimethicone so attractive to cosmetic manufacturers? It is, first of all, its incredible stability. Dimethicone does not go bad in cold or hot temperatures, it is not affected by UV-radiation, it stops bacterial and fungal reproduction, and it is environmentally friendly—what’s not to love?

Given all that, dimethicone itself has no impact on the skin. Its molecules are incapable of penetrating the skin and therefore of harming it. 

Add just a little bit of dimethicone to any cosmetic solution, and it will become more fluid, will spread on the skin easier and make it smooth to the touch. Among other things, dimethicone is a micro fluid—for example, the famous kinetic sand owes its unusual properties to dimethicone, and it only contains 2% of the substance. If your cream contains dimethicone, it’ll last longer, because you’ll only need a tiny bit of it for each application. If you add more dimethicone to a cosmetic solution, it will create a superfine film that lets through both air and water. These breathable films are used for damaged skin care solutions. They are good for dry skin as well because they let the skin’s natural protective barrier regenerate. However if you have normal healthy skin, you shouldn’t use dimethicone solutions regularly, because any substances that produce a film on your skin (including organic vegetable oil and wax) can suppress the synthesis of skin’s own lipids making healthy skin dry and temporarily unable to regenerate and protect itself.

Dimethicone is used for surgical prostheses and hydrogel contact lenses. It is added to sparkling drinks (helps control foaming), cooking oils (reduces splatter), shampoos and hair conditioners.

Few people know that dimethicone is successfully being used to get rid of lice — treatment solutions contain a large dose of dimethicone, it covers the hair with a silicon film under which the nasty parasites suffocate and die. The use of dimethicone has allowed to discard the toxic anti-parasitic substances that can be dangerous for little kids.

Nevertheless, there are some urban myths about dimethicone that are worth discussing separately.

  • Dimethicone clogs the pores causing the development of bacterial and fungi infection. False. In fact dimethicone suppresses the infection and it does not close the pores because the film it creates is very thin. However if the pores are noticeably large, they do get clogged easily, therefore using pore minimisers is necessary.
  • Dimethicone dries up the skin, because it stops the synthesis of its own lipids. Actually, dimethicone solutions are meant for dry and damaged skin, while healthy skin can in fact become drier after a few months of using them.
  • Dimethicone irritates the skin. No, it is absolutely neutral and practically never causes specific allergic reactions.
  • Dimethicone stops natural regenerating process. Yes, it is true, but it can be a very good thing when that regeneration is out of control—inflamed and irritated skin needs to “cool down” a bit. You simply should not use dimethicone solutions for healthy skin, not prone to dryness.
  • Dimethicone is bad for environment. When you cleanse your skin, dimethicone from a cream that you’d applied previously ends up in the water which is then cleaned in a standard way and is not polluted by it. Contact lenses and surgical prostheses are effectively recycled.

Numerous pieces of research have not found proof of any harmful effects from dimethicone. Even the strictest authorities, like the US FDA, Swiss and Japanese Ministries of Health have no objections to its use in cosmetics.

Originally published in “The Science of Beauty” by Dr Tiina Meder in 2015.

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