Should we adopt a silicone-free shampoo?

The silicones are ingredients commonly used in many hair care products, including shampoos, conditioners, and styling products. These are synthetic actives belonging to a family of polymers derived from silicon, a compound that naturally exists in sand.

The most common method for synthesising them is the polymerisation process, a chemical reaction that allows several monomer units to be linked to form long polymer chains. In the case of silicones, the monomers used are generally organosilicon compounds, that is, molecules containing both silicon atoms and organic groups.

In the formulation of cosmetic products, silicones are often found in the form of oil. In a shampoo or conditioner, these ingredients serve to coat the hair fibre to make it smooth and silky. They do not contribute to hair maintenance, as they merely cover the hair fibre with a film on the surface of the cuticle. They can be identified by their INCI name, which ends in -thicone, -thiconol, or -siloxane.

Just as silicones coat the hair, they also make it impervious to other treatments that need to be applied. Indeed, the build-up of silicones can prevent hair care products, such as masks, oils, and treatments, from properly penetrating the hair, thereby reducing their effectiveness.

Health risks?

It is crucial to note that silicones belong to a broad family of polymers, and not all necessarily have detrimental effects on health. Some silicones are entirely safe to use. However, there are specific types of silicones, such as theoctamethylcyclotetrasiloxane (D4) and the decamethylcyclopentasiloxane (D5), which can be toxic at high doses (>0.1%), a concentration from which they are likely to enter the systemic circulation. Indeed, they are suspected of being toxic to reproduction. Consequently, the European Regulation limits their concentration, which must be less than 0.1% by weight in cosmetic products to ensure their safety for human health.

And what about the environment?

Silicones pose a concerning environmental impact, as these chemically inert compounds require on average more than 400 to 500 years to degrade. Volatile silicones, such as D4 and D5, are particularly criticised, as they are known to accumulate in the environment and do not biodegrade due to their high stability.

However, this can lead to an increase in the concentration of these substances in ecosystems, which can be harmful to living organisms. Certain types of silicones, such as linear polymers, can be toxic to aquatic life, particularly fish and marine organisms. They can cause hormonal disruptions and adverse effects on marine organisms.

Note : Silicones are often portrayed as harmful to hair. However, at a concentration mandated by the European cosmetic regulation, this is not always the case. Indeed, by creating a protective layer on the surface of the hair, they play a crucial role in protecting against external aggressions.