Silicones: Why Are They Used? Review of Silicones in Hair Care, Skincare, and Cosmetics - The Dermatology Review

Silicones: Why Are They Used? Review of Silicones in Hair Care, Skincare, and Cosmetics

SKIN CARE REVIEWS

01.20.21DISCLAIMER

In recent years there has been a definite increase in consumers who are interested in the ingredients in their cosmetics products. With a highlight on health, wellness, and green beauty, it’s not uncommon for people to take a long hard look at the labels of some of their most favorite products and get a deeper understanding of what exactly those ingredients do. One of the most common and controversial ingredients of late are silicones.

So why the controversy? While silicones in cosmetics are considered safe for the skin, there’s some debate on whether or not they’re actually helping or simply masking the most common skin conditions. Opinions on silicones in cosmetics vary greatly and there is plenty of misinformation around. In order to make your own decision about silicones, you have to understand exactly what silicones are and how they work in your favorite cosmetics.

What Are Silicones?

Silicones are a skincare ingredient used to improve the texture and appearance of your skin. There are a few things that are useful to know about silicones when investigating why they’re in your skincare products. Silicones are organosiloxanes, which means that they are a molecule that has alternating silicon and oxygen atoms along a carbon chain or ring—silicones where originally sourced from sand in the form of silicon dioxide. 

There are three main categories of silicones that are used in cosmetic and skincare products. The first is small silicones, the second is silicone polymers or long-chain silicone molecules, and functional silicones which are characterized by their shape and structure. Most silicones can be identified by the end of their name. If an ingredient ends in -cone, -siloxane, or -conol, then it is probably a silicone. 

Small silicones
Small silicones are liquid and tend to evaporate from the skin. This makes them great for delivering key ingredients to the skin. However, they don’t have the same moisturizing abilities as some silicones.  An example of small silicones is cyclohexasiloxane. 

Silicone polymers
Silicone polymers are long-chain molecules and can be either liquid or solid; dimethicone is a silicone polymer. 

Functional silicones
Functional silicones usually contain other atoms outside of the oxygen, carbon, and silicon that are found in the other forms of silicone. These other atoms give them a different structure and tend to inform their properties. An example of functional silicones is dimethiconol. 

Why Are Silicones Used in Cosmetics

Silicones, at their most basic level, are a slippery substance that is derived from silica. They are characterized by their fluid properties and slippery texture, but also for their emollient and water-binding properties.

Silicones in cosmetics have been studied to help with a wide range of skin conditions and concerns. They are particularly helpful in soothing and healing capacities which enables them to be used in a variety of different products. 

Texture
Silicones are mainly used to improve the texture of products, helping to give the product a smooth, silky feel. The unique liquid texture of dimethicone allows for the product to be spread smoothly and evenly to the skin. 

Silicones generally don’t penetrate the skin, sitting on top, protecting the skin, and allowing smooth application and filling fine lines and wrinkles, helping the skin to appear smoother. This makes silicones an excellent ingredient for use in primers as the ability to fill texture and wrinkles improves makeup application.

 The texture of a product is mostly part of the sensory experience. However, it does also help to deliver the key ingredients of the product evenly to the skin and is useful in a product such as primers. 

Hydration and protecting
Silicones may also help to improve the appearance of dry skin and flakiness. Most silicones are occlusive to some degree. Occlusive means that it protects the skin and prevents moisture loss from the top layers of the skin. Moisturise can be lost from the top layers of the skin to the air and is also known as transepidermal water loss or TEWL.

 Occlusive products help to trap moisture and can help prevent the progression of skin conditions that occur when the skin barrier is disrupted, such as; eczema, dermatitis, and psoriasis. The skin barrier is the outer layers of the skin and includes the natural oils that the skin produces. When the skin barrier is damaged or disrupted from hormonal changes, irritation from other products, diet, or inflammation, it can cause the skin to lose moisture, leaving the skin dry and flaky. A healthy skin barrier helps to protect the skin from harmful bacteria and allergens. 

Silicone’s emollient properties can help to soothe the skin and give the appearance of hydration without the greasy residue that other hydrating ingredients leave behind

Due to the protective and hydrating properties that silicones have, it is often included in formulations for mild skin irritations, diaper rashes, and some formulations used to help heal minor wounds and cuts. The dimethicone in these products coats the skin and not only adds moisture to the affected area but also helps to seal moisture in providing a better healing environment for the skin. 

Breakouts
Silicones may also help to prevent breakouts. There is a lot of misinformation around silicone products and congestive skin types, with many people claiming that they can clog the pores and create an environment that produces breakouts and worsens acne. However, there is no evidence to suggest that this is the case, silicones are classified as non-comedogenic and non-acnegenic, meaning that it doesn’t clog the pore or worsen acne. Research has indicated that it helps provide hydration to the skin without the use of heavier hydrating ingredients. Hydration is essential for congested skin types to prevent sebum overproduction and inflammation associated with dryness. Dimethicone also controls shine in oily complexions. 

The idea that silicones are bad for clogged pores may come from the fact that it is occlusive, meaning that it acts as a protective barrier to the skin. If silicones aren’t used correctly and properly cleansed from the skin after exercise or heavy sweating, it is possible to trap sweat between the skin and the silicone-containing product, potentially causing congestion. Silicone-containing products may also push other skincare products and ingredients deeper in the skin when they have been used before a silicone-based product. This may also contribute to congested skin as other ingredients may cause irritation and breakouts, mainly when they are pushed deeper into the skin. 

Scars
Research into silicones has suggested their use in improving the appearance of scars. A study published in the Journal of Cutaneous and Aesthetic Surgery determined that silicone gel preparations significantly reduces the appearance of superficial, hypertrophic, and keloid scars.  Many of the silicone gel preparations used for scarring contain a mixture of a number of different silicones.  

Haircare
Silicones are also an excellent ingredient for hair care products, like conditioners and leave-in serums. Silicones are thought to offer a controlled conditioning effect to leave unhealthy, damaged hair looking, and feeling more silky and smooth. Additionally, silicones are widely used in hair cuticle coating products due to their ability to help with problems such as split-ends. Silicones work by reducing the friction between the hair shafts. This reduction in friction means that damage to the hair shaft is limited and also has the added benefits of limiting flyaways and adding shine. 

Efficacy
Silicones may also help to improve the efficacy of the product that it is contained in. As silicones may help other ingredients to penetrate deeply into the skin, this can help key ingredients or ‘actives’ to work more effectively. 

What Are The Main Silicones Used In Skincare?

There are countless different types of silicones in cosmetics but the most common are cyclopentasiloxane and dimethicone. These two silicones are found most commonly in hair care, creams, and other skincare products.

Other silicones include dimethiconol, cyclohexasiloxane, cyclomethicone, amodimethicone, phenyl trimethicone, the list goes on. Silicones are a large class of ingredients and are widely used in both skincare, hair care and cosmetics. 

Silicones: The Controversy 

With all of the benefits that silicones in cosmetics provide, it’s interesting to note that there are so many who believe that using silicones like cyclopentasiloxane and dimethicone can actually worsen many skin conditions. Some of these claims include that silicones clog pores, can cause acne, lead to dull and dehydrated skin, and even affect the skin cells’ natural regeneration process. In essence, silicones in cosmetics have been claimed to actually suffocate the skin rather than provide the benefits.

 While these claims are understandable, and in some cases seem to make sense, it should be noted that all the silicones used in cosmetics have been approved and deemed safe for people to use. Many of these concerns or controversies are actually a case of misinformation. We will get into some of the misunderstandings and truths about silicone below.

The Truth About Silicones

Natural vs. Synthetic
One of the main criticisms of silicones is that they are synthetic ingredients. There is a stigma around synthetic ingredients in the skincare world, particularly in the green or natural beauty industry. 

While the idea that natural ingredients are better does seem appealing, it isn’t necessarily true. Many natural ingredients can cause irritation and sensitize the skin and many synthetic ingredients are beneficial and safe for the skin. Silicones are one such ingredient. 

Breakouts and Congested Skin
Silicones have often been accused of clogging pores and worsening congestive skin types. This is because silicones are occlusive ingredients, forming a protective barrier on the surface of the skin.  However, in the extensive research that was reviewed by the Cosmetic Ingredient Review Expert Panel and the US Food and Drug Administration, dimethicone, the most commonly used silicone and the silicone which is generally considered to clog the pores, was found to be non-comedogenic and non-sensitizing, meaning that it doesn’t clog pores or cause irritation. 

Key ingredients
Silicones have faced criticism that they may reduce the ability of the skin to absorb ‘active’ ingredients from skincare products. The opposite has been indicated in the studies conducted to date. Research suggests that silicone-containing products may actually help key ingredients to penetrate deeply into the skin, allowing them to work more effectively to improve the appearance of the skin.

Hair loss
Another myth about silicones is that when included in hair care products, it prevents the follicle from obtaining oxygen, resulting in hair loss. Again, this is a myth where the truth is the opposite. Silicone products help to coat and smooth the hair follicle, giving it a shiny appearance and making it easier to comb through. When the hair follicle is covered in silicones, it is less prone to friction and there less likely to be affected by breakage from styling or combing.

Environment
An essential area of skincare that has come to the forefront in recent years is the impact that the industry has on the environment. Silicones as a class of ingredient have been criticized in this area because they are not biodegradable. While this is true, silicone and dimethicone are filtered out of the water as the clay can trap the undissolved ingredients. Clay filtration of dimethicone and silicones degrades the silicone and is a natural chemical-free way to prevent silicones from entering the environment. 

Allergies and Irritation
Allergies and irritation have been linked with silicones. There is no scientific evidence to support this claim. While there are a handful of anecdotal cases of irritation to dimethicone, it is more likely, given the lack of actual evidence, that these cases are reacting to other ingredients in the dimethicone containing products. Dimethicone is too large to penetrate the skin to produce an allergy or irritation. As is the case with most silicones, however, some are more likely to irritate than others. 

Safety
The safety of silicones has come under question with claims that it is toxic and accumulates in the body. Silicones generally have undergone extensive research across many countries’ regulatory authorities. In the US, the Cosmetic Ingredient Review Expert Panel reviewed the available safety data for many of the silicones that are used in skincare, hair care and cosmetics and determined that they are safe for its indicated uses.

This outcome has been echoed by the US Food and Drug Administration, the EU’s Inventory of Cosmetic Ingredients group, and the World Health Organisation. Most silicones have strict concentrations and guidelines to follow when the are used in a formulation. 

Silicone Alternatives

Although the research surrounding silicones in cosmetics is extensive, there are people who’d rather not use them or  risk negatively impacting the environment. For companies catering to these consumers, they may turn to dimethicone and cyclopentasiloxane alternatives. Natural based silicone alternatives are a popular option with vegetable glycerin being one of the first that brands try. Some limitations with a natural-based silicone alternative are cost and performance during the formulation process. There are some synthetic silicone alternatives available that companies may choose to try in an effort to decrease the number of silicones inside their products that provide the same benefits as the silicones without some of the worries. And in the middle are silicone alternatives that are synthetically made to mimic natural alternatives that hope to provide cosmetics with the best of both worlds.

References:
Johnson, W et al., 2012. ‘Safety Assessment of Cyclomethicone, Cyclotetrasiloxane, Cyclopentasiloxane, Cyclohexasiloxane, and Cycloheptasiloxane’, International Journal of Toxicology, vol. 30, pp. 149-227.

Burgess, I, Lee, P & Brown, C, 2008. ‘Randomised, controlled, parallel-group clinical trials to evaluate the efficacy of isopropyl myristate/cyclomethicone solution against head lice’, Pharmaceutical Journal, vol. 280, pp. 371-375.
De Paepe, K, Sieg, A, Le Meur, M & Rogiers, V 2014. ‘Silicones as Nonocclusive Topical Agents, Skin Pharmacology and Physiology, vol. 27, pp. 164-171. 
Disapio, A & Fridd, P, 1988. ‘Silicones: use of substantive properties on skin and hair’, International Journal of Cosmetic Science, vol. 10, is. 2, pp. 75-89.Brown, A & Barot, L, 1986. ‘Biologic Dressings and Skin Substitutes’, Journal of Clinical Plastic Surgery, vol. 13, is. 1, pp. 69-74.
Van Reeth, I 2006. ‘Beyond Skin Feel: Innovative Methods for Developing Complex Sensory Profiles with Silicones’, Journal of Cosmetic Dermatology, vol.5, is. 1, pp.61-67
Puri, N & Talwar, A, 2009. ‘The Efficacy of Silicone Gel for the Treatment of Hypertrophic Scars and Keloids’, Journal of Cutaneous and Aesthetic Surgery, vol. 2 is. 2, pp. 104-106.
Gobas FA et al., Fugacity and activity analysis of the bioaccumulation and environmental risks of decamethylcyclopentasiloxane (D5) (open access), Environ Toxicol Chem. 2015, 34, 2723-2731. 
Carter, B & Sherman, R, 1957. ‘Dimethicone (Silicone) Skin Protection in Surgical Patients’, Archives of Surgery, vol. 75, is. 1, pp. 116-117.
Cosmetic Ingredient Review, 2019. ‘Safety Assessment of Dimethicone, Methicone and Substituted-Methicone Polymers, as Used in Cosmetics’, Cosmetic Ingredient Review Expert Panel.
Englert, C et al., 2018. ‘Pharmapolymers in the 21st century: Synthetic polymers in drug delivery applications’, Progress in Polymer Science, vol. 87, pp. 107-164.
Kwon, S, et al., 2013. ‘The effect of glycerin, hyaluronic acid and silicone oil on the hydration, moisturization and transepidermal water loss in human skin’, Korean Journal of Aesthetic Cosmetology, vol. 11, pp. 761-768.
Mojsiewicz-Pieńkowska, K et al., 2016. ‘Direct human contact with siloxanes (silicones)- safety or risk: Part 1 Characteristics of siloxanes (silicones), Frontiers in Pharmacology, vol. 7, pp. 132.
Pellicoro, C, Marsella, R, & Ahrens, K, 2013. ‘Pilot study to evaluate the effect of topical dimethicone on clinical signs and skin barrier function in dogs with naturally occurring atopic dermatitis’, Veterinary medicine international. 
Yahagi, K, 1992. ‘Silicones as conditioning agents in shampoos’, Journal of the Society of Cosmetic Chemists, vol. 43, pp. 275-284.

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