Dimethiconol is a silicone-based compound widely used in the cosmetic industry, particularly in skincare and haircare products. It is known for its film-forming and protective properties, helping to enhance texture, softness, and moisture protection. Similar to dimethicone but with a modified structure, Dimethiconol creates a protective barrier that helps retain moisture in the skin and improves shine and manageability in hair.

Chemical Composition and Structure

Dimethiconol is a silicone polymer, consisting of a siloxane backbone with hydroxyl (OH) end groups. This unique chemical structure allows Dimethiconol to form a protective film on the skin and hair, enhancing hydration and shielding from environmental damage. Unlike dimethicone, Dimethiconol has terminal OH groups, making it slightly more flexible and reactive.

Physical Properties

It is typically a clear, viscous liquid that is insoluble in water but compatible with other silicone-based substances and cosmetic oils. Its ability to form a protective barrier makes it ideal for use in products designed to prevent moisture loss and protect the skin and hair from environmental stressors.

Production Process

Dimethiconol is synthesized through the polymerization of siloxanes, with the addition of terminal hydroxyl groups. This process creates a stable polymer chain, giving the compound its unique protective and film-forming characteristics. After production, it is refined to ensure high purity and effectiveness in cosmetic formulations.

The name defines the structure of the molecule:

• "Di-" refers to the presence of two Methicon units in the polymer.
• "Methicone" is a term used to describe a group of polymer silicones.
• The termination "-ol" indicates the presence of a hydroxyl (-OH) group at the end of the polymer chain.

The synthesis process takes place in several stages:

• Silicon extraction: Silicon is extracted from sand or quartz silica, usually through a process that involves heating with carbon in an electric furnace.
• Polymerization: The extracted silicon is reacted with methyl chloride (CH3Cl) at high temperature and pressure to form a mixture of methyl chlorosilans. These are then hydrolyzed and condensed to form a polymer with repeated Methicon units.
• Final block: The polymer chain is then blocked at the end with a hydroxyl group (-OH) to form dimethicone. This is usually done by reacting the polymer with a compound that contains a hydroxyl group.
• Purification: The resulting dimethiconol is purified to remove all unreacted materials and impurities. This is typically done through distillation or filtration.
• End product: Purified dimethicone is packaged and stored for use in various applications, such as cosmetics and personal care products where it is used for its lubricating and moisturizing properties.

What it is used for and where it is used

Cosmetics

Antifoaming agent. The constituent factors for foam stabilisation are the concentration of nanoparticles and hydrophobicity. Foam, even when used in separation operations such as fractionation or flotation, can cause a decrease in density and a deterioration in quality in cosmetic products. The defoaming agent (non-polar oil, silicone oils, hydrophobic solid particles or mixtures of both) is strongly influenced by viscosity and, to an almost directly proportional extent, concentration. However, defoamers can carry an irreversible source of contamination.

Skin conditioning agent - Emollient. Emollients have the characteristic of enhancing the skin barrier through a source of exogenous lipids that adhere to the skin, improving barrier properties by filling gaps in intercorneocyte clusters to improve hydration while protecting against inflammation. In practice, they have the ability to create a barrier that prevents transepidermal water loss. Emollients are described as degreasing or refreshing additives that improve the lipid content of the upper layers of the skin by preventing degreasing and drying of the skin. The problem with emollients is that many have a strong lipophilic character and are identified as occlusive ingredients; they are oily and fatty materials that remain on the skin surface and reduce transepidermal water loss. In cosmetics, emollients and moisturisers are often considered synonymous with humectants and occlusives.

Health and Safety Considerations

Safety in Use

Dimethiconol is considered safe for use in cosmetics and personal care products. It is non-toxic, non-irritating, and non-sensitizing, making it suitable for sensitive skin. It is widely used for its film-forming and protective properties without clogging pores or causing irritation.

Allergic Reactions

Allergic reactions to Dimethiconol are extremely rare. However, as with any cosmetic ingredient, it is recommended to perform a patch test before using new products to rule out any individual sensitivities.

Toxicity and Carcinogenicity

It is widely regarded as safe in cosmetic and personal care products when used at recommended concentrations.

Environmental and Safety Considerations

As a silicone-based compound, Dimethiconol is chemically stable and does not degrade easily in the environment. However, silicones like Dimethiconol can accumulate in the environment, which is why it’s important to use silicone-containing products responsibly and consider biodegradable alternatives when possible.

Regulatory Status

Dimethiconol is approved for use in cosmetics and personal care products by regulatory agencies such as the European Union and the Food and Drug Administration (FDA) in the United States. It is subject to regulations to ensure consumer safety.

References__________________________________________________________________________

Johnson W Jr, Heldreth B, Bergfeld WF, Belsito DV, Hill RA, Klaassen CD, Liebler DC, Marks JG Jr, Shank RC, Slaga TJ, Snyder PW, Andersen FA. Safety Assessment of Dimethiconol and Its Esters and Reaction Products as Used in Cosmetics. Int J Toxicol. 2017 Nov/Dec;36(3_suppl):31S-50S. doi: 10.1177/1091581817739429. 

Abstract. Dimethiconol and its esters and reaction products are used in cosmetics as either skin-conditioning agents or hair-conditioning agents. The Cosmetic Ingredient Review (CIR) Expert Panel reviewed relevant data and concluded that these ingredients are safe in the present practices of use and concentration described in this safety assessment. While there is an absence of data on reproductive and developmental toxicity and limited tumorigenicity and toxicokinetics data, the Panel reasoned that these ingredients would not be absorbed through the skin, obviating concern over potential reproductive and developmental toxicity or carcinogenicity.

Izri A, Uzzan B, Maigret M, Gordon MS, Bouges-Michel C. Clinical efficacy and safety in head lice infection by Pediculus humanis capitis De Geer (Anoplura: Pediculidae) of a capillary spray containing a silicon-oil complex. Parasite. 2010 Dec;17(4):329-35. doi: 10.1051/parasite/2010174329. 

Abstract. Head lice are endemic worldwide. Resistance to permethrin and doubts about the safety of pesticides promoted the use of physical therapies (wet-combing, dry-on suffocation). The aim of our study was to test the pediculicidal and ovicidal effects of one application of a silicon-oil complex composed of dimethiconol and castor oil. The study was a prospective cohort of 108 infested patients (11 males, 97 females; 58 children, 50 adults), in Sri-Lanka. Pediculicidal efficacy was evaluated as the percentage of patients free of live lice one hour after the application of the treatment and at day 1 (wet combing). Ovicidal efficacy was calculated as the proportion of subjects without larval stages at days 1 and 7 among subjects followed up all over the study. In normal conditions of use, in this open cohort, a pediculicidal effect of a dimethiconol-castor-oil lotion was.shown one hour after application in 99/108 (91.7%) treated subjects and at day 1 in 86/99 (87%) subjects and an ovicidal effect at day 7 in 79/108 (73.2%) treated subjects. A second application of the same product was necessary to increase the cure rate to 79.6% (86/108) at day 8. In our study, the second application of the same product was performed seven days later, but the best time for additional applications should be defined in further studies. However, the efficacy of this safe physical treatment was similar to that of chemical pediculicides (malathion, permethrin).