With or without Silicones? A Comprehensive Review of Their Role in Hair Care Free

Silicones, unique polymers defined by their repeating siloxane bonds (Si–O–), have established themselves as essential components in the hair care industry due to their protective properties [1, 2]. These versatile agents are widely incorporated into shampoos, conditioners, styling products, and treatments. Silicones create a thin film over the hair shaft, effectively reducing friction during combing, preventing moisture loss, and imparting a noticeable shine [2‒4].

However, despite these advantages, critics highlight concerns regarding product buildup, particularly from water-insoluble silicones, and the environmental implications of certain cyclic silicones. Recent innovations in silicone technology, including water-dispersible and nano-encapsulated systems, aim to address these issues while maintaining key benefits such as enhanced hair texture and protection against thermal and chemical damage [3, 5, 6]. This article provides a comprehensive review of the classification, advantages, and controversies surrounding silicones, offering evidence-based insights tailored for dermatologists, trichologists, and cosmetic scientists.

A literature review was undertaken to investigate the role of silicones in hair care, focusing on their formulation strategies, physicochemical properties, and impact on hair structure and cosmetic performance. The methodology adhered to the principles established by the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines.

A comprehensive search was conducted across the PubMed and Google Scholar databases, encompassing publications from January 1988 to February 2024, with a particular emphasis on those published in the last decade. Earlier references were included only when they were deemed essential for supporting fundamental concepts, providing historical context, or offering unique insights that enhanced the relevance of the review. The keywords used were: “silicone” OR “silicones” combined with “hair care”. The search was restricted to articles published in English.

Inclusion criteria were as follows: original research articles, literature reviews, clinical or cosmetic studies, and relevant narrative reports that directly addressed the use, behavior, safety, efficacy, or formulation of silicones in hair care. Studies that concentrated on industrial silicones, silicone prostheses or implants, or any routes of administration other than topical applications were excluded. Additionally, research on silicones unrelated to hair care or cosmetic use was also omitted from consideration.

After screening and eligibility assessment, ten articles were included in the final synthesis. In addition, three book chapters were selected due to their relevance, technical depth, and frequent citation in the indexed literature. These chapters were manually identified through targeted search using publisher websites, Google Books, and bibliographic cross-referencing. Notably, the inclusion of these chapters was crucial to cover essential formulation aspects and application strategies not fully covered in the primary research articles.

Silicones in hair care products can be categorized based on solubility, volatility, or specific functional groups [1, 2, 7, 8]. Water-insoluble silicones, such as dimethicone, amodimethicone, and cyclomethicone, offer robust film-forming and conditioning effects; however, they may lead to accumulation if not properly cleansed [2, 4]. In contrast, water-soluble silicones, like dimethicone copolyol, rinse out more effectively, reducing concerns about residue [7, 9]. Volatile silicones, including cyclomethicone and cyclopentasiloxane, evaporate after application, delivering a lightweight finish without leaving behind any residue [2, 7].

Additionally, amino-functional silicones, such as amodimethicone, exhibit a unique capability to selectively bind to the most damaged areas of the hair shaft through electrostatic interactions, providing targeted conditioning [2]. Ongoing innovations focus on combining these functional groups, exemplified by the emergence of fourth-generation silicones, which often incorporate nanotechnology to offer more precise and environmentally conscious solutions [3, 5, 6].

Silicones are categorized by their generational development, reflecting advancements in formulation and application. The first generation comprises basic silicones, such as dimethicone, which provide protection and shine while being water-insoluble. This characteristic can lead to product buildup, particularly on fine or oily hair [1, 2]. The second generation introduced modified silicones, exemplified by amodimethicone, which selectively target damaged areas of the hair, thereby enhancing compatibility across diverse hair types [2, 7]. The third generation is marked by the emergence of multifunctional silicones, including silsesquioxanes, which offer thermal protection, volume enhancement, and wash resistance. These characteristics help mitigate buildup and improve environmental compatibility [2, 3, 7]. The fourth generation encompasses nano-structured and encapsulated silicones, which are engineered for controlled deposition, reduced environmental impact, and improved stability in advanced formulations [3, 5, 6, 10]. Collectively, these innovations reflect a significant shift toward more customized and eco-friendly strategies in hair care technology.

Silicones offer numerous benefits in hair care, primarily through their film-forming and protective effects. They create a uniform, protective layer around each hair strand, which reduces mechanical stress during combing and heat styling while also acting as a barrier against humidity, thus helping to maintain hairstyles and minimize frizz [2, 4, 11]. Additionally, silicones improve hair texture and appearance by smoothing the cuticle, which reduces roughness and makes hair easier to detangle and style; for instance, phenyl trimethicone is particularly effective in enhancing shine and color longevity, which is especially beneficial for chemically treated hair [2, 4, 12]. Moreover, modified silicones, such as siloxy siloxanes, contribute to esthetic enhancement by increasing volume and improving texture, resulting in a fuller, healthier look, particularly in products designed for fine or limp hair [2, 3, 7]. Silicones also demonstrate compatibility with various treatments; in medicated shampoos that contain active ingredients like zinc pyrithione or selenium sulfide, they can mitigate the drying effects of these compounds, thereby enhancing consumer tolerance [13]. Furthermore, silicones reduce friction for bleached or dyed hair, leading to decreased breakage rates [7, 12]. By providing a conditioning layer, they also enhance the sensory experience of these products, promoting adherence to therapeutic regimens.

The disadvantages and controversies surrounding silicones in hair care primarily revolve around buildup concerns, removal challenges, and environmental impact. Prolonged use of water-insoluble silicones, such as dimethicone, can lead to accumulation on the hair shaft [3, 4]. While clarifying shampoos containing sulfates, like sodium lauryl sulfate, are often employed to eliminate this residue, excessive usage may result in dryness or even damage to the cuticle [9, 13]. Moreover, the removal of water-insoluble silicones requires strong surfactants, which can be harsh on delicate or textured hair, potentially leading to dryness and brittleness. Therefore, it is essential to balance the benefits of silicones with their removal requirements, particularly for sensitive hair types [7, 13]. Additionally, cyclic silicones raise environmental concerns due to their low biodegradability, which can contribute to pollution and bioaccumulation [3]. In response, regulatory bodies have placed restrictions on their use in cosmetics, prompting manufacturers to explore alternative ingredients [4]. However, newer silicone variants, including water-dispersible and nano-based formulas, aim to reduce ecological footprints without compromising cosmetic performance [3, 5, 6]. The latest findings from the Cosmetic Ingredient Review panel have concluded that cyclomethicones (D4, D5, D6, and D7) are safe as cosmetic ingredients at specified concentrations. As the beauty industry increasingly shifts toward sustainability, the development of eco-friendly silicone alternatives remains a crucial priority.

Practical guidance for the use of silicones in hair care emphasizes the importance of product selection, preventing excessive buildup, and tailoring choices to individual hair types. Fourth-generation products that incorporate nanotechnology are particularly recommended for their targeted deposition, sustained release, and reduced environmental impact, as these formulations enhance protection, conditioning, and shine while minimizing product wastage [3‒6, 14]. To avoid excessive silicone accumulation, it is advisable to alternate between silicone-based and silicone-free products [7], to use clarifying shampoos periodically, especially for fine or oily hair, to effectively remove residues and restore vitality without compromising hair health [9, 13]. Some experts advocate that the use of clarifying agents, followed by silicone-based shampoos or conditioners, may be especially advantageous for individuals with chemically treated or dyed hair. This approach not only aids in the removal of product buildup but also helps preserve moisture and enhance manageability.

Tailoring products to specific hair types can further optimize results; for fine or limp hair, volatile or water-soluble silicones are preferable to preserve volume [2, 7], while thicker or coarse hair benefits from heavier silicones that provide enhanced smoothness and hydration [4]. For curly or textured hair, amino-functional and water-dispersible silicones can improve definition and reduce dryness [2, 7, 15]. Additionally, it is essential to educate patients about the benefits of silicones, such as damage prevention, manageability, and shine enhancement, while addressing common myths, such as the misconception that silicones “suffocate” hair. It is important to explain their role in forming a breathable barrier and to emphasize the necessity of proper usage, including thorough rinsing and moderation in the application of styling products to prevent residue buildup.

Silicones are valuable in trichology, providing protection, conditioning, and esthetic benefits. Their effectiveness relies on appropriate formulation and personalized application for individual hair types. Dermatologists play a crucial role in guiding balanced usage, promoting clarifying treatments, and selecting suitable silicone formulations. While research addresses long-term environmental concerns, silicones remain a reliable hair care solution when used wisely and with expertise. This balance between efficacy and environmental responsibility ensures that silicones continue to be a beneficial option in hair care.

Dr. Antonella Tosti acts as consultant for DS Laboratories, Almirall, Thirty Madison, Eli Lilly, Pfizer, Myovant, Bristol Myers Squibb, Ortho Dermatologics, Sun Pharmaceuticals, LLC, PI Eli Lilly, and Concert and was also a member of the journal’s Editorial Board at the time of submission. The other authors have no conflicts of interest to declare.

This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors.

D.F.M. conceived the manuscript. R.M.C. performed literature search and wrote the manuscript. A.K. and A.T. revised the manuscript. All authors approved the final version.