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Moumoujus

TRANS-2-HEXENAL.

Questionable CAS 6728-26-3 / PERFUMING

TRANS-2-HEXENAL is a naturally occurring aldehyde found in various plants, where it serves as a volatile signaling compound to activate defense responses. In the cosmetic industry, its primary application is as a fragrance ingredient due to its distinctive scent profile. However, its formulation requires precise handling given its established potential as a skin sensitizer at certain concentrations.

Summary

Fragrance

Science

Mechanism of Action

Naturally present in plants, TRANS-2-HEXENAL acts as an airborne signaling chemical, upregulating plant defenses and demonstrating inhibitory effects on fungal pathogens. In human skin, its chemical structure suggests it can initiate and activate the initial key events (1, 2, and 3) of the skin sensitization Adverse Outcome Pathway (AOP). Its primary function in cosmetic products is to impart fragrance.

Research

Clinical Evidence

Insufficient-data confidence
Effective range N/A
Optimal

N/A

Transparency

Dusting Analysis

Commonly dusted
Min. effective
18 µg/cm2%

TRANS-2-HEXENAL is a common fragrance component, but it is considered a skin sensitizer above a Weight of Evidence No Expected Sensitization Induction Level (WoE NESIL) of 18 µg/cm2. Clinical studies observed sensitization effects in 6 out of 25 subjects at a concentration of 236 µg/cm2, indicating a clear red flag for concentrations exceeding the established safety threshold.

The Formula

Formulation

Solubility
Oil
Optimal pH N/A
0 7 14

Stability

This ingredient is a flammable liquid and vapor, with vapors capable of forming explosive mixtures with air. Aldehydes like TRANS-2-HEXENAL can form diethylacetals when in alcoholic solutions, which may compromise their intended efficacy. It must be stored and formulated away from heat, hot surfaces, sparks, open flames, and other ignition sources.

Conflicts

  • Oxidizing agents
  • Pyrophoric or self-heating substances
  • Heat
  • Hot surfaces
  • Sparks
  • Open flames
  • Ignition sources
  • Alcoholic solutions (may form diethylacetals)

Safety

Safety Profile

CIR Status
Not reviewed
Max tested
18 μg/cm2%
Sensitization risk Moderate

TRANS-2-HEXENAL is considered a skin sensitizer with a Weight of Evidence No Expected Sensitization Induction Level (WoE NESIL) of 18 µg/cm2. Studies show no sensitization at 4% concentration or at 18-23 µg/cm2, but sensitization was observed in a human maximization test at 236 µg/cm2. Concentrations below 4% are not anticipated to be irritating to human skin. It is approved for use as a food additive but is subject to restrictions in cosmetics under Annex III of the EC Cosmetics Regulation following assessment by the SCCS.

Your Skin

Skin Compatibility

No Normal
No Dry
No Oily
No Sensitive
Irritancy Medium
Comedogenicity Unknown

Our Assessment

Verdict

Questionable

While a naturally occurring compound and a common fragrance, TRANS-2-HEXENAL's established potential for skin sensitization at concentrations above 18 µg/cm2 makes its inclusion in precision skincare products highly questionable.

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