Silicones in hair care

Key takeaways

• Silicones are water-repellent polymers that coat the hair surface, cut friction, add slip and shine, and are the main reason many conditioners and serums feel silky. They do not repair damage inside the fibre. They mask it and reduce the mechanical stress that causes more. Carvalho 2025
• Not all silicones behave alike. Water-insoluble types (dimethicone, cyclopentasiloxane) can build up, amino-functional types (amodimethicone) are designed to stick to damaged hair, and PEG-modified types disperse in water.
• Buildup is real but mostly a product-choice and washing issue. Stronger surfactants are needed to remove insoluble silicones, and over-clarifying can cause dryness. Carvalho 2025
• Silicone-free conditioners reached comparable relubrication and combing results on bleached hair in one supplier-run study, so silicones are a convenience, not a necessity. Liu 2022
• Safety: the Cosmetic Ingredient Review panel judged dimethicone and the amino-silicones safe as used, with minimal absorption. Nair 2003 The concern is environmental, mostly for volatile cyclic silicones (D4, D5, D6), which the EU now limits.
• "Silicones suffocate hair" and "silicones cause hair loss" have no support in anything we found. The fibre is dead keratin, and scalp buildup is a hygiene question (see dimethicone).

The science

What they are: polymers built on a repeating siloxane backbone, sold as fluids, gums, volatile cyclic oils and modified versions carrying amine, hydroxyl or polyether groups. Carvalho 2025

What they do on the fibre: atomic force microscopy found that silicone type, deposition level and the cationic surfactant used all change nanoscale friction and adhesion of hair. La Torre 2006 Bleaching strips the natural fatty layer, raising wettability and friction (the strawy feel). Relubricating the surface, with or without silicone, lowers friction and reduces combing work. Liu 2022

Where they stick: on virgin hair deposition is driven mainly by hydrophobic interaction, and on bleached hair electrostatic interaction matters most. Labarre 2023 That is why positively charged amino-silicones are positioned for damaged hair (see amodimethicone).

Shine: a Kao study reported that a shampoo and conditioner system with amino-silicone formed a very fine surface structure that raised colour intensity and shine and helped dyed hair keep its look. It is manufacturer research, not independently replicated. Watanabe 2007

What it means for your hair

• High-porosity, bleached or heat-damaged hair sees the most visible benefit from slip and sealing, and amino-silicones suit it best. Evidence is instrumental, not clinical.
• Fine, low-density hair is weighed down by dimethicone-rich leave-ins. Use small amounts on the lengths only.
• Curly and coily hair (3A-4C): silicones cut friction and frizz by touch, but buildup can leave curls limp. Clarify on a schedule if you use them (inference from the buildup data).
• Low-porosity hair: product sits on the surface, so buildup risk is higher with leave-ins.
• Oily or itchy scalp: keep silicone-rich products off the scalp.

Myths and facts

Bottom line

Use a silicone conditioner or serum for slip, shine and friction protection, concentrated on mid-lengths and ends. If hair feels coated or stops absorbing moisture, an occasional clarifying wash is reasonable, followed by conditioner. On labels look for dimethicone, dimethiconol, amodimethicone, cyclopentasiloxane, PEG-12 dimethicone and bis-aminopropyl dimethicone. Heat protection from silicone films has limits (see heat damage). In the EU, D5 and D6 are restricted in cosmetics.