Alcohol Denat.
Also known as Denatured alcohol, Denatured ethanol, SD Alcohol, Alcohol denat
“CIR Expert Panel says: restricted.”
The 2008 CIR Expert Panel final report (IJT 27 Suppl 1:1-43) is the primary authoritative assessment. The panel's verdict is denaturant-dependent: Alcohol Denat. formulations denatured with t-Butyl Alcohol, Denatonium Benzoate, Diethyl Phthalate, or Methyl Alcohol are concluded safe as used; those denatured with Quassin, Brucine, or Brucine Sulfate lack sufficient safety data. Lachenmeier (2008) reviewed topical ethanol safety more broadly, noting ethanol on intact skin does not cause acute systemic toxicity in adults but can transiently disrupt the stratum corneum lipid barrier and act as a penetration enhancer; individuals with aldehyde dehydrogenase deficiency show heightened irritation sensitivity.
At concentrations typical in cosmetics (under ~40%), ethanol is an effective solvent, penetration enhancer, and antimicrobial vehicle
When denatured with approved denaturants (especially Denatonium Benzoate or t-Butyl Alcohol), Alcohol Denat. produces formulas with desirable sensory properties: fast-evaporating, lightweight, low residue
CIR concluded safe as used for the most commercially prevalent denatured forms (SD Alcohol 40-B with Denatonium Benzoate is the predominant variant in modern cosmetics)
No evidence of systemic toxicity in healthy adults from topical exposure at typical cosmetic use concentrations
- · Topical ethanol can transiently extract stratum corneum lipids, increasing skin permeability and acting as a penetration enhancer for co-formulants
- · Individuals with aldehyde dehydrogenase (ALDH) deficiency experience heightened irritation and contact dermatitis from topical alcohol exposure
- · SD Alcohol 39 and 40 (denatured with Quassin/Brucine) remain without a positive CIR safety conclusion as of the 2008 report
CIR verdict is denaturant-dependent: the UNS (unsafe/not-supported) classification applies to Alcohol Denat. denatured with Quassin, Brucine, or Brucine Sulfate due to reproductive toxicity (Quassin) and CNS toxicity (Brucine) signals in rodent studies
Consumer perception controversy: Alcohol Denat. is frequently flagged in 'clean beauty' discourse as drying or damaging; the science distinguishes between short-contact rinse-off use (minimal concern) and heavy leave-on use (possible barrier disruption with repeated exposure), a distinction consumer-facing ingredient databases often collapse
CIR Quick Reference Table (September 2022) — Alcohol Denat. row: Finding=UNS, Citation=IJT 27(Suppl. 1):1-43, 2008
“Alcohol Denat. | UNS | The CIR Expert Panel concluded that Alcohol Denat.... denatured with t-Butyl Alcohol, Denatonium Benzoate, Diethyl Phthalate, or Methyl Alcohol are safe in the practices of use and concentration as described in this safety assessment, and, that Denatonium Benzoate is safe as a denaturant. The CIR Expert Panel concluded that the available data are insufficient to support the safety of Alcohol Denat.... denatured with Quassin, Brucine, and Brucine Sulfate in cosmetic products, and that the available data are insufficient to support the safety of Quassin, Brucine, and Brucine Sulfate as denaturants. | IJT 27(Suppl. 1):1-43, 2008”— QuickReferenceTable_AllConclusionTypes.pdf, p. 17