Encyclopedia · silicone
Dimethicone
The standard hair silicone, a water-insoluble oil that coats the fibre for slip, shine and friction control without repairing anything.
What it is
A fluid mixture of fully methylated linear silicone polymers. In the Cosmetic Ingredient Review it was used as a conditioning agent at up to about 15%. Nair 2003
How it works
It forms a water-repellent lubricating film. Friction and adhesion on hair vary with silicone type and deposition level. La Torre 2006 It is not strongly attracted to hair and is deposited with the help of cationic surfactants and polymers. On bleached hair, electrostatic forces matter more. Labarre 2023
What the studies show
- Silicone type and deposition level changed nanoscale friction and adhesion on hair. La Torre 2006
- On bleached hair, conditioning restored water repellency and cut combing work, and a silicone-free emulsion was comparable (BASF-affiliated study). Liu 2022
- A 2025 review found the film reduces friction and moisture loss, with buildup concerns. Carvalho 2025
- No controlled human-scalp trials of dimethicone for hair health were found. The evidence is instrumental data only.
How it's used in studies
Rinse-off conditioners and leave-in serums, at concentrations up to 15% in the safety review. Nair 2003
Side effects and safety
The safety review found it not absorbed through skin or by mouth, minimally irritating, not a sensitiser in a 5% patch test of 83 people and negative for genotoxicity, and judged it safe as used. Nair 2003 The practical issue is buildup with insoluble types, which then need stronger cleansing. Carvalho 2025 It is a cosmetic ingredient in the US, EU and UK.
Bottom line
Useful for frizz, shine, detangling and ends, especially on damaged or coarse hair. Skip heavy use on fine, low-density or low-porosity hair, and keep it off an oily scalp. Silicone-free alternatives also work in tests. We are moderately sure about surface effects and unsure about any claim beyond them. See silicones.
Studies 5
Nair B, Cosmetic Ingredient Review Expert Panel. Final report on the safety assessment of stearoxy dimethicone, dimethicone, methicone, amino bispropyl dimethicone, aminopropyl dimethicone, amodimethicone, and related silicones. Int J Toxicol. 2003
Result: The panel judged dimethicone and the amino-silicones safe as used in cosmetics, with minimal absorption.
Read the study ↗La Torre C, Bhushan B. Nanotribological effects of silicone type, silicone deposition level, and surfactant type on human hair using atomic force microscopy. J Cosmet Sci. 2006
Result: Silicone type, deposition level and the cationic surfactant used all changed nanoscale friction and adhesion of hair.
Read the study ↗Labarre L et al. Hair surface interactions against different chemical functional groups as a function of environment and hair condition. Int J Cosmet Sci. 2023
Result: Hydrophobic interaction drove deposition on virgin hair and electrostatic interaction on bleached hair.
Read the study ↗Liu Z et al. Effects of cosmetic emulsions on the surface properties of Mongolian hair. ACS Omega. 2022
Result: Bleaching raised wettability and friction; emulsions containing conditioning agents restored water repellency and reduced combing work.
Read the study ↗Carvalho RM, Melo DF, Kelati A, Tosti A. With or without silicones? A comprehensive review of their role in hair care. Skin Appendage Disord. 2025
Tested: silicones in hair care
Result: Silicones reduce friction, prevent moisture loss and add shine and heat protection, with build-up concerns for water-insoluble types; newer water-dispersible forms exist.
Read the study ↗Related
- AmodimethiconeA dimethicone with positively charged amine groups, so it clings to damaged hair and resists rinsing better than plain dimethicone.
- CyclopentasiloxaneA volatile silicone that spreads easily and evaporates, used to carry heavier silicones in serums; now restricted in the EU for environmental reasons.
- DimethiconolA dimethicone with hydroxyl end groups, usually supplied as a thick gum emulsion for longer-lasting slip in rinse-off conditioners.
- PEG-12 dimethiconeA dimethicone with polyethylene glycol side chains that makes it water-dispersible, so it rinses out more easily than classic silicones.
- Silicones in hair careSilicones coat hair to cut friction and add shine without repairing it; buildup is real but manageable, and the scare claims are unsupported.