Science
Mechanism of Action
It functions by targeting and breaking the disulfide (cystine) bonds that provide structural integrity to hair keratin. In an alkaline environment (typically pH 11.5–12.5), the molecule penetrates the hair cortex, weakening the fiber until it can be easily wiped away. This process is often supported by pH adjusters that swell the hair shaft for better penetration.
Research
Clinical Evidence
High confidence4%
Key findings
- 01 Concentrations above 4% show diminishing returns in depilatory efficacy while significantly increasing the risk of skin irritation.
- 02 An 8% concentration has been shown to remove coarse beard hair within 6 minutes when formulated in a stabilized trihydrate matrix.
- 03 Standard efficacy for keratin bond dissolution is established within the 2-10% range according to SCCS assessments.
Transparency
Dusting Analysis
This is a functional active rather than a claim ingredient; using it below 2% would likely render a depilatory product ineffective. Because it is highly irritating, it is rarely 'dusted' in standard skincare, but must be present at specific thresholds to perform its hair-removal function.
The Formula
Formulation
Stability
Highly sensitive to acidic environments and thermal stress; should not be heated above 40°C. Requires specific packaging such as glass, PE, or ceramics as it can react with certain plastics.
Synergies
- Calcium Hydroxide
- Sodium Hydroxide
- Glycerin
Conflicts
- Acids
- Oxidizing agents
- Natural oils
- Polar solvents
Safety
Safety Profile
While CIR allows up to 15.2% in hair straighteners, the EU SCCS limits depilatory use to 5% due to the high pH required for activity. Use is strictly time-limited to prevent chemical burns.
Your Skin
Skin Compatibility
Our Assessment
Verdict
An essential and highly effective hair-removal agent that requires precise formulation and strict adherence to contact time to manage its high irritation potential.
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References
Sources