Silicones are among the most effective ingredients in conventional hair care. They coat the hair shaft with a thin, water-repellent film that immediately reduces frizz, increases shine, and makes hair feel smooth. They are also excluded from every COSMOS certified formula, and understanding why requires looking at what they actually do over time.
What Silicones Are
Silicones are a family of synthetic polymers derived from silicon, a naturally occurring element, combined with oxygen, carbon, and hydrogen. In hair care, they appear under names including Dimethicone, Cyclopentasiloxane, Cyclohexasiloxane, Amodimethicone, Phenyl Trimethicone, and Dimethiconol, among others.
They are petroleum-process derived: silicon is extracted from silica (sand) through an energy-intensive industrial process involving carbon and high heat. The resulting silicone polymers are synthetic compounds with no natural equivalent. This is the primary reason they are prohibited under the COSMOS standard, which requires all ingredients to be of natural origin.
What They Do to Hair
Silicones work by coating the hair cuticle with a hydrophobic film. This film:
- Seals the cuticle surface, making it feel smooth and look shiny
- Reduces friction between hair strands (less frizz, easier detangling)
- Creates a barrier against humidity (temporary frizz control)
- Adds apparent weight to fine strands, which can reduce volume
The results are immediate and perceptible after a single use. This is why silicones are so widely used: they produce reliable cosmetic results.
The Buildup Problem
Most silicones used in hair care are not water-soluble. Dimethicone, the most common, does not rinse away with water alone. Over repeated use, it accumulates on the hair shaft and, critically, on the scalp, around follicle openings.
This accumulation has two practical effects. First, it can block the hair shaft from receiving moisture from conditioning treatments, since the silicone layer repels water-based ingredients. The hair may feel smooth but can become progressively drier underneath the coating. Second, accumulation at the scalp can interfere with follicle health over time and may contribute to product buildup that raises scalp pH and disrupts microbial balance.
Removing silicone buildup requires a clarifying or sulphate-containing shampoo, because milder surfactants do not break the hydrophobic film. This creates a cycle where conventional hair care products, silicone conditioner followed by sulphate shampoo, are partly designed to manage the effects of each other.
Water-Soluble Silicones
Some silicones, such as Cyclomethicone and certain PEG-modified silicones, are water-soluble and rinse away more easily. These are sometimes considered less problematic from a buildup perspective, though they are still synthetic and excluded from COSMOS formulas. Their environmental profile is also a consideration: volatile cyclic silicones such as Cyclopentasiloxane (D5) have been identified as persistent environmental contaminants and are subject to EU regulatory restrictions.
What We Use Instead
COSMOS certified formulas achieve smoothing, shine, and frizz control through naturally-derived alternatives: plant oils (which condition without building up), hydrolysed proteins (which smooth the cuticle surface), and plant-based conditioning agents that are biodegradable and water-soluble.
The results differ from silicones: there is no instant heavy coating, and the hair's condition tends to improve progressively rather than becoming dependent on a coating agent that masks underlying dryness.
All NUDA products are formulated without silicones. Browse our Shine and Colour collection for naturally-derived gloss alternatives, or our Volume and Body collection for lightweight conditioning without silicone weight. Full certification details at certifications.
The shine shampoo is one example of that approach: it builds shine through plant oils and hydrolysed proteins instead of a silicone coating.
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- Clarifying Shampoo: Do You Actually Need One?
Frequently Asked Questions
Are silicones harmful to hair?
Silicones are not acutely harmful to the hair or scalp. The concerns are primarily about long-term buildup, moisture blocking, and scalp accumulation with repeated use. For some hair types, particularly low-porosity or fine hair, silicone buildup can become problematic over time. For others, the cosmetic benefits outweigh the concerns. The choice depends on individual hair type and how frequently clarifying is done.
Why are silicones excluded from COSMOS certified formulas?
The COSMOS standard requires all ingredients to be of natural origin and processed using approved methods. Silicones are synthetic compounds produced through industrial chemistry with no natural equivalent. They also do not meet COSMOS biodegradability requirements, certain silicones are classified as persistent environmental contaminants.
How do I know if a product contains silicones?
Check the INCI ingredient list for any ingredient ending in "-cone", "-conol", "-siloxane", or "-silane". Common ones include Dimethicone, Cyclopentasiloxane, Amodimethicone, Cyclohexasiloxane, and Phenyl Trimethicone. If you see any of these, the product contains silicones.
Do I need to clarify before switching to silicone-free products?
If you have been using silicone-containing products regularly, a clarifying wash before switching to a silicone-free routine can help remove accumulated buildup and give the new products a clean surface to work with. Without clarifying first, natural conditioning ingredients may not penetrate as effectively through existing silicone layers.
Do silicone-free products work as well for frizz?
They work differently. Silicones create an immediate physical barrier against humidity. Natural alternatives, plant oils, hydrolysed proteins, plant-derived conditioning agents, work by improving the hair's own moisture retention and cuticle condition. The initial cosmetic effect may be less dramatic, but the underlying hair condition typically improves over time rather than becoming dependent on the coating.