Silicones – Quest for Truth – Part One

by Barbara Bird CMG

Silicone ingredients are among the most maligned, most demonized, of all hair care ingredients. They have been so thoroughly (and effectively) attacked by beauty bloggers and natural care websites that some pet shampoo manufacturers will deny using them or have stopped saying that they use them.


A quick chemistry lesson: While silicon is a natural element, silicones are not natural. All silicones are synthesized and man made. What makes silicones so interesting and infinitely variable is that they are polymeric. Polymers are long chained molecules complexes of repeating links.

Silicones have a backbone of repeating silicon-oxygen (Si-O) links. Varying the length of the polymer chain allows chemists to create a wide variety of properties.

Silicone polymers are made further complex by the attachment of other components to the basic repeating silicon-oxygen backbone, such as vinyl, phenyl, or methyl groups. This allows nearly infinite variation.

Silicones can be fluids, resins, gums, or rubbers. In hair care, most of the silicones are liquid.(1)


DIMETHICONE – Also referred to as Polydimethylsiloxane (PDMS), dimethicone oils are the most commonly found silicones in pet grooming products. Dimethicone is one of the most often used conditioning ingredients in 2-in-1 shampoos, aka conditioning shampoos.

An often-cited study by Kazuyuki Yahagi in 1992 clearly demonstrated the superiority of Dimethicone to other conditioners in reducing combing forces.(2)

The Wacker Company, a leading silicone supplier, has determined that a two percent silicone ingredient in a two-in-one conditioning shampoo can reduce the dry combing force by 75 percent.(3)

Dimethicones are available as low, medium and high viscosity fluids.  High viscosity dimethicone fluids are better suited to add sheen and manageability to hair care products than lower viscosities. They are among the most commonly used conditioning additives.

Here are the features of high viscosity dimethicones as presented by Clearco, another major silicone supplier:

  • High Viscosity
  • Excellent Lubrication
  • Low Surface Tension: High Spreadability
  • Provides a soft, emollient feel to skin
  • Prevents stickiness in skin care products
  • Compatible with a wide range of solvents
  • Hydrophobic: water repellent
  • Inert- improves stability and shelf-life of formulations
  • Increase body & shine in hair care products
  • Seal-in moisture: prevent hair damage.(4)

DIMETHICONOL – Dimethiconol is a mixture of siloxane polymers referred to as polydimethylsiloxane terminated with hydroxyl (-OH) groups. Dimethiconol can be combined with other molecules, such as the amino acids (arginine, cysteine and methionine) or fatty acids (behenic acid, stearic fatty acids from meadowfoam seed oil) or other compounds to form derivatives of Dimethiconol that are useful as cosmetic ingredients.(5)  An example would be Dimethiconol Panthenol.

Dimethiconols have superior lubricity and conditioning effects. They are often utilized as blends with cyclomethicones or other substances to offer solutions to formulating difficulties that might be experienced with dimethicones. The silicone industry is very solutions oriented and is constantly developing new ingredients designed to solve or avoid problems faced in using older ingredients.

DIMETHICONE COPOLYOLS – This family of silicones that is made from a process of ethoxylation of Dimethicone with polyoxyethylene and/or polyoxypropylene in order to create a water-soluble silicone.  These substances can be identified by having PEG and/or PPG in the ingredient INCI name, such as PEG-8 Dimethicone, PEG/PPG-20/23 Dimethicone. The number represents the number of moles of ethylene oxide or propylene oxide attached to the polymer. The higher the number of moles, the greater the solubility.(6)

In shampoos and conditioners, the water soluble feature makes for easier formulation, but there is considerably less conditioning effect as more is rinsed off. Because they are nonionic and compatible with anionic detergent surfactants, the Copolyols are a good choice for conditioning shampoos. Some Dimethicone Copolyols are also emulsifiers and surfactants in personal care products.

PHENYL DIMETHICONE – This type of silicone is unique for its high refractive index, which translates into the ability to create high gloss and incredible shine.(7)  In grooming products, it is found in leave-in sprays, hair serums and “silk drops.”

AMINE-FUNCTIONALIZED SILICONES – Usually labeled as Amodimethicone or Trimethylsilylamodimethicone, this family of silicones has been modified to be more substantive to the hair.  They have been made more cationic and have a positive ion charge that is strongly attracted to the negative charge that exists on the surface of the wet hair shaft. Since the sites on the hair shaft where there is cuticle damage carry a stronger negative charge, the cationic conditioner deposits more conditioner molecules to these sites, very effectively filling in the spaces of the hair cuticle. This makes amine-functionalized silicones well-suited for conditioning treatments, and allows formulators to maximize the conditioning ability of a product with a lesser quantity of silicone ingredient(s).(8)

Since canine hair is often more porous and more negatively charged, especially curly coats and soft undercoat, amine- functionalized silicones are a good fit for dog grooming products. These silicones have also been engineered to resist build up, as the molecules do not layer or attach to themselves.(9)(10)

CYCLOMETHICONES – This silicone family is made of cyclic, rather than linear molecular chains.  There are three types of cyclomethicones, Cyclotetrasiloxane (D4), Cyclopentasiloxane (D5) and Cyclohexasiloxane (D6). The cyclomethicones are known as “volatile” silicones. Due to their volatility (varying rates of evaporation), low surface tensions (high spreadability), and non-greasy feel, Cyclomethicones are used as base fluids, carrying agents and wetting agents in a wide range of personal care products, including hair products. Because they evaporate rather quickly, they are most often found in combination with other silicones, such as Dimethicone or Dimethiconol, which they deliver to the substrate (hair or skin). They are also the diluents for hair serums and silk drops products.

All three types of cyclomethicones are approved as safe for cosmetic use in the U.S., E.U, and Canada, although some animal studies have raised potential health issues in regards to D4, and D4 is also under investigation as an environmental hazard in the EU and Canada.(12)(13)(14)

Unfortunately, the issues raised by studies of D4 cyclomethicone have been used by fear mongers to indict the entire body of silicone cosmetic ingredients.  We will review these issues in greater depth in Part II of the series on Silicones: A Quest for Truth – Safety Issues & Environmental Concerns. Stay tuned!

QUATERNIZED SILICONES (Silicone Quats) – In studying the action of how silicones act on the hair, cosmetic scientists observed that Amodimethicone had greater affinity to hair when formulated along with Cetrimonium Chloride, a popular quaternized conditioner (quat).  Silicone suppliers began offering the two ingredients in a blended emulsion. Never satisfied to leave well-enough alone, the next step for silicone chemists was to create a polymer where the two could be combined in a single molecule. Voila! Silicone Quats were born and have become popular players in human hair care. This latest generation of silicones offers the best ever substantivity to hair and resistance to breakage.(15)

PROTEIN/SILICONE COPOLYMERS – Hydrolyzed Wheat Protein PG-Propyl Silanetriol and Cystine Bis-PG- Propyl Silanetriol are advanced copolymers of proteins and silicone that offer proven protection against cuticle damage caused by common hairstyling practices such as blow drying, combing and styling.

Due to their complex polymeric structure, these polymers cross-link on drying to form a conditioning and protective network that offers exciting functional benefits to hair care products.(16)

The protection created by the cross-linkage is referred to as “heat activated” conditioning benefits.

The incorporation of natural protein structures into the silicone polymer molecule is the trend of creating more “natural” silicone ingredients to meet the powerful market demand in the human beauty industry. While silicone quats and protein/silicone copolymer ingredients are rare in grooming products, the competitive nature of the industry will ultimately result in the utilization of these newer, more sophisticated conditioning ingredients.


One thing that struck me about truth and myths regarding cosmetic ingredients, including silicones, is how much work and expense goes into supporting manufacturers claims and how little it takes to create a negative myth.   Hair breakage is a good example.  In the world of human hair care products, when a company makes a claim that their product reduces hair breakage or prevents hair breakage, they must be able to substantiate that claim.  Chemical suppliers such as Dow Corning, Wacker, and Evonik do extensive testing at great expense to prove the effects of their ingredients. (9)(10)(15) 

A myth or negative claim, however, costs nothing.  It only needs to be repeated.  A good indication that a negative claim is baseless myth, is finding the same phrases being repeated on many websites or blogs.

Silicones are occlusive. One such phrase is that silicones coat the hair “much like plastic wrap”, “suffocating” it and causing it to dry out and subsequently break.(17)  This statement is offered over and over on lists of ingredients to avoid. No evidence is offered, often no reference is made, or the reference is a so-called “expert” who simply offers the assertion.

An expert who may have been the originator of this myth is Chrystn Nawrot, a Regional Educator for Phyto Hair Care Products, who was quoted in Marie Clair Magazine in January 2006, “While silicone products are great at preventing frizz and enhancing shine, do not apply them before heat-styling, or they can fuse to your hair and have a ‘shrink wrap’ effect, sapping all the moisture from your strands.” (18)

These experts often have allegiance to a company that is marketing a “no silicone” approach. Phyto Hair Care is such a company. The claim that silicones are occlusive is simply false. One of the primary properties of silicone fluids is that they form a permeable layer on the hair and skin. This means that silicones seal in moisture while allowing the skin to breathe.

Silicones build up and can’t be washed from hair. Let’s talk about build up! This is one of the biggest complaints against silicones in hair products, and it has some basis in fact. Except for the Dimethicone Copolyols, most silicone ingredients are not soluble in water. This had lead to the belief that silicones are not removed by washing and will build up over time. This is not exactly true.

The ability of a conditioning ingredient to adhere to the surface of the hair is called its “substantivity.”  In order to replace the natural sebum that has been removed during the cleansing process, it is desirable to have ingredients which coat the hair shaft and resist being rinsed off.  Considerable research and development has gone into creating conditioning ingredients that have greater substantivity with less weight to the hair shaft.

Build-up occurs when ingredients that are very substantive to the hair accumulate to the point of causing negative effects. Under normal use, most substantive ingredients are washed off with regular shampoo.  That is they WERE, until the trend toward sulfate-free ultra mild shampoos and conditioner shampooing (“co-washing”). Instead of blaming the shampoos for not doing the job of removing residue, they blame the conditioning ingredients for doing the job of adhering to the hair.

News Flash: Silicones are not the only ingredients that can build up on the hair. Silicones get the blame, but any of the quaternized conditioning ingredients (quats and polyquats), such as Cetrimonium Chloride and Polyquaternium-10 will stick to the hair and have potential for build-up as well.  Although some beauty bloggers make a big to-do over the fact that most silicones are not water-soluble and blame this for build-up, the truth is that substantivity (to hair) not solubility (in water) is more of a factor. The products that have the greatest potential for build-up are styling products, not shampoos or conditioners.

Shampooing with a well-formulated sulfate shampoo will generally remove any residue from previous conditioning or styling efforts.


Here is my view of the benefits of Silicones in pet grooming products:

  • Improves straightening effect by smoothing hair cuticle.
  • Helps hair resist humidity and re-curl.
  • Aids detangling and brush out.
  • Facilitates deshedding by adding slip to hair and reducing static cling in the coat.
  • Protects hair from thermal damage from heat drying.
  • Allows hair to be dried and shaped with less heat application.
  • Adds shine and glow to all coat types.
  • Provides conditioning without over softening.
  • Creates a breathable film that seals in essential moisture to hair cortex and prevents moisture loss.
  • Protects hair cuticle from damage by brushing and combing.
  • Stabilizes foaming in products to reduce rinsing time (saves time, conserves water)
  • Significantly decreases drying time of all coat types. (saves time, conserves electricity)


We have seen that the chemistry of silicones allows for continual invention and evolution of products. State-of-the-art of silicone technology continues to drive forward with the creation of new polymers that have enhanced benefits and solve the problems of yesterday. The ingredients of today are not the same as twenty years ago when silicones first entered the pet grooming arena. Misconceptions and misinformation remain stuck due to continued recycling over the Internet. Instead of covering up and hiding the use of silicones in grooming products, we would encourage manufacturers to own their silicones and join the effort to educate users.

In Part II of Silicones, A Quest for Truth, we will review safety issues surrounding silicone ingredients, including various health issues and environmental concerns. Do silicones cause cancer and birth defects? Will they destroy the planet? Stay tuned, we are “going there.”


Click here for Part Two  ♦