PEG-12 Dimethicone: properties, uses, INCI functions, safety, alternatives

PEG-12 Dimethicone is a chemical compound, derived from silicone, a chemically inert polymer based on silicone. It comes in the form of a colorless transparent liquid.  The prefix ''dimeth'' recalls the two methyl groups that are attached to the silicone molecule to form dimethicone. At high temperatures it behaves as a viscous liquid, while at low temperatures it assumes a rubbery behavior.  It is resistant to water and UV rays.

The name defines the structure of the molecule:

"PEG-" stands for polyethylene glycol, a polymer based on ethylene oxide. The number that follows "PEG-", in this case 12, indicates the average number of ethylene glycol units in the PEG molecule. Therefore, PEG-12 would have an average of 12 ethylene glycol units.
"Dimethicone" is a type of silicone used for its lubricating and conditioning properties. It is a polymer made up of repeating dimethylsiloxane units, which is a compound consisting of silicon, oxygen, and methyl groups.

The synthesis process takes place in several stages:

Stage 1: Preparation of raw materials: dimethicone and polyethylene glycol.
Stage 2: Reaction. Dimethicone reacts with polyethylene glycol in the presence of a catalyst. This reaction links the polyethylene glycol chains to the dimethicone backbone.
Stage 3: Purification. The resulting PEG-12 Dimethicone is purified to remove any unreacted raw materials and by-products through a series of washing and filtration steps.
Stage 4: Drying. The purified PEG-12 Dimethicone is then dried to remove any residual solvent.

Industrially it is produced in different formats that are distinguished by a number indicating the nominal kinematic viscosity placed after the name. The number appearing after the abbreviation PEG represents the molecular weight and the higher this number is, the less it penetrates the skin.

Dimeticone BP (Poly(dimethylsiloxane)  CAS 9006-75-9

Dimethicone USP (-(Trimethylsilyl)- -methylpoly[oxy(dimethylsilylene) CAS 9006-65-9  [–(CH₃)₂SiO–]n

What it is for and where

It acts as an emulsifier and is used in the cosmetic industry in liquid soaps, shampoos and more. It is a non-neurotoxic topical agent. It is often used in hair products both for its hydrophobic feature that makes the hair smooth and for its high molecular weight that, on the skin, prevents the penetration of exogenous substances, protecting the skin. At concentrations between 1% and 30% it is considered safe. It is mainly an emulsifier and in tablets it has the function of antifoaming.

Hair conditioning agent. A significant number of ingredients with specific and targeted purposes may co-exist in hair shampoo formulations: cleansers, conditioners, thickeners, matting agents, sequestering agents, fragrances, preservatives, special additives. However, the indispensable ingredients are the cleansers and conditioners as they are necessary and sufficient for hair cleansing and manageability. The others act as commercial and non-essential auxiliaries such as: appearance, fragrance, colouring, etc. Hair conditioning agents have the task of increasing shine, manageability and volume, and reducing static electricity, especially after treatments such as colouring, ironing, waving, drying and brushing. They are, in practice, dispersants that may contain cationic surfactants, thickeners, emollients, polymers. The typology of hair conditioning agents includes: intensive conditioners, instant conditioners, thickening conditioners, drying conditioners. They can perform their task generally accompanied by other different ingredients.

Skin conditioning agent. It is the mainstay of topical skin treatment as it has the function of restoring, increasing or improving skin tolerance to external factors, including melanocyte tolerance. The most important function of the conditioning agent is to prevent skin dehydration, but the subject is rather complex and involves emollients and humectants that can be added in the formulation.

Other uses

Industrial Lubricants - Its combined hydrophobic and hydrophilic properties can make PEG-12 Dimethicone useful in certain lubricant formulations.

Surfactant in Cleaning Agents - Its surfactant properties can help in removing oils and residues in industrial cleaning processes.

Textile Industry - It can be used as an additive to provide a soft finish to fabrics and to help with the uniform distribution of other chemicals during fabric processing.

Agriculture - It can be employed as a spreader or wetting agent for agricultural sprays to ensure even distribution and coverage of pesticides or herbicides on plants.

De-foaming Agent - Silicone derivatives like PEG-12 Dimethicone can act as antifoaming agents in industries where foam can be problematic, such as in certain manufacturing processes.

Ink and Coatings - The compound can help modulate the flow and spreading properties of inks and coatings.

Medical Devices - In some contexts, silicone derivatives can be used in medical device manufacturing, either as part of the device material or as a lubricant.

Alternatives

Most significant studies

Dimethicone is considered to be a safe and highly effective treatment for lice in pediatrics (1) definitely better than permethrin.

Effective in the treatment of Actinic Keratoses on the face (2).

Effective in the management of reflux oesophagitis (3).

Safety

Safe as used in cosmetic formulations (4).

For more information:

Dimethicone studies

Typical characteristics of commercial product Octamethyltrisiloxane (Dimethicone)

• Molecular Formula : C₈H₂₄O₂Si₃
• Linear Formula: [(CH₃)₃SiO]₂Si(CH₃)₂
  
• Molecular Weight : 236.533 g/mol
• CAS : 9016-00-6  107-51-7  9006-65-9   556-67-2
• UNII 9G1ZW13R0G
• EC Number: 203-497-4
• DSSTox Substance ID: 
• MDL number  MFCD00008264
• PubChem Substance ID 24870584
• InChl  1S/C8H24O2Si3/c1-11(2,3)9-13(7,8)10-12(4,5)6/h1-8H3
• InChI Key      CXQXSVUQTKDNFP-UHFFFAOYSA-N
• SMILES    C[Si](C)(C)O[Si](C)(C)O[Si](C)(C)C
• IUPAC dimethyl-bis(trimethylsilyloxy)silane
• ChEBI    9147
• NACRES  NA.23

Synonyms :

• Octamethyltrisiloxane
• Octamethyl-Trisiloxane
• Polydimethylsiloxane
• Dimethicone
• Polidimetilsilossano
• Poly(oxy(dimethylsilylene)), alpha-(trimethylsilyl)-omega-methyl-
• Trisiloxane, 1,1,1,3,3,5,5,5-octamethyl-
• alpha-(Trimethylsilyl)-omega-methylpoly(oxy(dimethylsilylene))
• Dimethyl polysiloxane, dimethyl-terminated
• Dimethylbis(trimethylsilyloxy)silane
• dimethyl-bis(trimethylsilyloxy)silane
• Dimethyl polysiloxane, bis(trimethylsilyl)-terminated
  
  

References____________________________________________________________________

(1)  Ihde ES, Boscamp JR, Loh JM, Rosen L. Safety and efficacy of a 100% dimethicone pediculocide in school-age children. BMC Pediatr. 2015 Jun 20;15:70. doi: 10.1186/s12887-015-0381-0. Erratum in: BMC Pediatr. 2016;16:12.

(2) Jim On SC, Hashim PW, Nia JK, Lebwohl MG. Assessment of Efficacy and Irritation of Ingenol Mebutate Gel 0.015% Used With or Without Dimethicone Lotion for Treatment of Actinic Keratosis on the Face. J Drugs Dermatol. 2017 May 1;16(5):432-436. 

(3) Smart HL, Atkinson M. Comparison of a dimethicone/antacid (Asilone gel) with an alginate/antacid (Gaviscon liquid) in the management of reflux oesophagitis. J R Soc Med. 1990 Sep;83(9):554-6. 

(4) Becker LC, Bergfeld WF, Belsito DV, Hill RA, Klaassen CD, Liebler DC, Marks JG Jr, Shank RC, Slaga TJ, Snyder PW, Andersen FA. Safety Assessment of Dimethicone Crosspolymers as Used in Cosmetics. Int J Toxicol. 2014 May;33(2 suppl):65S-115S. doi: 10.1177/1091581814524963. 

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And a premise on PEG.

Since the PEG (1) family is numerous and is found in many cosmetic, cleaning and medicinal products and others, we need a cognitive premise on the subject that is rather complex from the point of view of safety because these products not only come into contact with the skin but, as in the case of medicine, they are also ingested.

PEG or polyethylene glycols polymerise the condensed ethylene oxide and water and are called polyethylene glycols, but in reality, they are complex chemical components, polymers bound together. For example,  plastic is polyethylene and has a hard consistency, while  polyethylene aggregated to the glycol forms a liquid.

The number that appears after the initials PEG represents the molecular weight and the higher this number is, the less it penetrates  the skin. 

Here below are some studies in Medicine that refer to the use of PEG Polyethylene glycol in various fields.

Intestine

Polyethylene glycol with or without electrolytes is effective for the treatment of functional constipation, both in adults and in paediatric patients, with great safety and tolerability. These preparations are the most effective osmotic laxatives (more than lactulose) and are the first-line treatment for functional constipation in the short- and long-term. They are as effective as enemas in faecalomas, avoid the need for hospitalisation and are well tolerated by patients (especially when given without electrolytes) (2).

In the preparation  for colonoscopy,  polyethylene glycol tablets confirmed efficacy, acceptability, tolerance and safety similar to those of sodium phosphate (3).

For peripheral nerve repair (4).

Eyes

Dry eye syndrome is a disorder that affects 5-34% of the world's adult population with reduced quality of life. Artificial or lubricating tears are the most used therapy for treating this condition due to their low side effects profile, which attempt to modify the properties of the tear film. Polyethylene glycol has demonstrated clinical efficacy in the treatment of this condition (5).

Brain

Polyethylene glycol facilitates the neuroprotective effects of magnesium in head injuries (6).

Tumors

For transarterial chemoembolization, Polyethylene glycol is effective and safe for the treatment of liver cancer, as indicated by good tolerability, quality of life and high tumour response (7). 

Cosmetics

Many types of PEG are hydrophilic and are used as creams, topical dermatological preparations and in cosmetic products such as surfactants, emulsifiers, detergents, humectants and skin conditioners.

Safety varies from type to type given the structural complexity (8).

References___________________________________________________________________

(1) Fruijtier-Pölloth C. Safety assessment on polyethylene glycols (PEGs) and their derivatives as used in cosmetic products. Toxicology. 2005 Oct 15;214(1-2):1-38. doi: 10.1016/j.tox.2005.06.001.

(2) Mínguez M, López Higueras A, Júdez J. Use of polyethylene glycol in functional constipation and fecal impaction. Rev Esp Enferm Dig. 2016 Dec;108(12):790-806. doi: 10.17235/reed.2016.4571/2016.

Santos-Jasso KA, Arredondo-García JL, Maza-Vallejos J, Lezama-Del Valle P. Effectiveness of senna vs polyethylene glycol as laxative therapy in children with constipation related to anorectal malformation. J Pediatr Surg. 2017 Jan;52(1):84-88. doi: 10.1016/j.jpedsurg.2016.10.021.

(3) Chaussade S, Schmöcker C, Toulemonde P, Muñoz-Navas M, O'Mahony V, Henri F. Phosphate tablets or polyethylene glycol for preparation to colonoscopy? A multicentre non-inferiority randomized controlled trial. Surg Endosc. 2017 May;31(5):2166-2173. doi: 10.1007/s00464-016-5214-1.
Tsunoda T, Sogo T, Iwasawa K, Umetsu S, Oikawa-Kawamoto M, Inui A, Fujisawa T. Feasibility and safety of bowel cleansing using low-volume polyethylene glycol with ascorbic acid before pediatric colonoscopy: A pilot study. Dig Endosc. 2017 Mar;29(2):160-167. doi: 10.1111/den.12756.

(4) Hoffman AN, Bamba R, Pollins AC, Thayer WP. Analysis of polyethylene glycol (PEG) fusion in cultured neuroblastoma cells via flow cytometry: Techniques & optimization. J Clin Neurosci. 2017 Feb;36:125-128. doi: 10.1016/j.jocn.2016.10.032.

(5) Pérez-Balbuena AL, Ochoa-Tabares JC, Belalcazar-Rey S, Urzúa-Salinas C, Saucedo-Rodríguez LR, Velasco-Ramos R, Suárez-Sánchez RG, Rodríguez-Carrizalez AD, Oregón-Miranda AA. Efficacy of a fixed combination of 0.09 % xanthan gum/0.1 % chondroitin sulfate preservative free vs polyethylene glycol/propylene glycol in subjects with dry eye disease: a multicenter randomized controlled trial. BMC Ophthalmol. 2016 Sep 20;16(1):164. doi: 10.1186/s12886-016-0343-9.

Labetoulle M, Messmer EM, Pisella PJ, Ogundele A, Baudouin C. Safety and efficacy of a hydroxypropyl guar/polyethylene glycol/propylene glycol-based lubricant eye-drop in patients with dry eye. Br J Ophthalmol. 2017 Apr;101(4):487-492. doi: 10.1136/bjophthalmol-2016-308608.

(6) Busingye DS, Turner RJ, Vink R. Combined Magnesium/Polyethylene Glycol Facilitates the Neuroprotective Effects of Magnesium in Traumatic Brain Injury at a Reduced Magnesium Dose. CNS Neurosci Ther. 2016 Oct;22(10):854-9. doi: 10.1111/cns.12591.

(7) Aliberti C, Carandina R, Sarti D, Mulazzani L, Catalano V, Felicioli A, Coschiera P, Fiorentini G. Hepatic Arterial Infusion of Polyethylene Glycol Drug-eluting Beads for Primary and Metastatic Liver Cancer Therapy. Anticancer Res. 2016 Jul;36(7):3515-21.

(8) Jang HJ, Shin CY, Kim KB. Safety Evaluation of Polyethylene Glycol (PEG) Compounds for Cosmetic Use. Toxicol Res. 2015 Jun;31(2):105-36. doi: 10.5487/TR.2015.31.2.105.