Get a Free 5ml Mini Now Free 5ml Mini With Every Order of The Mantle
Moumoujus

TOLUENE-2,5-DIAMINE.

Avoid CAS 95-70-5 / HAIR DYEING

Toluene-2,5-Diamine is an oxidative hair dye ingredient primarily utilized for permanent hair colorants. Despite its effectiveness in hair dyeing, it presents a significant risk profile due to its potent sensitizing and irritating properties, rendering it inappropriate for direct application in precision skincare formulations.

Summary

Hair Dyeing

Science

Mechanism of Action

This compound functions as an oxidative hair dye, acting as a coupler. It reacts with hydrogen peroxide and other dye precursors to form colored molecules that subsequently penetrate the hair shaft, effectively altering hair color.

Research

Clinical Evidence

Medium confidence
Effective range N/A
Optimal

N/A

Key findings

  1. 01 Induced strong local inflammation, with T and B cell infiltration and proliferation observed in draining lymph nodes when incorporated into a hair dye gel.
  2. 02 Prompted skin inflammation, albeit with only minor responses detected in the draining lymph nodes when part of a hair dye gel formulation.
  3. 03 Identified as a sensitizer in patch testing.
  4. 04 Reported as not being a dermal irritant in a specific study, though other evidence suggests otherwise.
  5. 05 Demonstrated a total absorption of 3.41% +/- 1.32% in human skin samples when formulated with a coupler and hydrogen peroxide.

Transparency

Dusting Analysis

Not commonly dusted

Toluene-2,5-Diamine is not an ingredient typically used for its benefits in precision skincare, nor is it commonly 'dusted' at low percentages to achieve specific cosmetic effects on the skin.

The Formula

Formulation

Solubility
Water
Optimal pH N/A
0 7 14

Stability

Toluene-2,5-Diamine and its sulfate demonstrate stability for up to 8 days in aqueous and water:acetone (4:1, v/v) solutions at ambient temperature, provided they are stored away from light. Stability data specific to typical hair dye formulations were not reported.

Conflicts

  • Bases (reacts as an acid)
  • p-Phenylenediamine (PPD) due to high risk of cross-reactivity and allergic contact dermatitis

Safety

Safety Profile

CIR Status
Safe with restrictions
Max tested
4.0% (free base) / 7.2% (sulfate salt) on-head (for hair dye use)%
Sensitization risk High

The Cosmetic Ingredient Review (CIR) Expert Panel concluded Toluene-2,5-Diamine and its sulfate are safe for use as hair dye ingredients under present practices and concentrations (up to 3% and 4% respectively in products), with a caution regarding its potential as a sensitizer. In stark contrast, the Scientific Committee on Consumer Safety (SCCS) in 2007 deemed its use unsafe based on available data, identifying it as an 'extremely potent skin sensitiser'. European Union regulations restrict its use in oxidative hair dyes to a maximum of 10% as a free base in the finished product, with an intended maximum on-head concentration of 4.0% (free base) or 7.2% (sulfate). Toluene-2,5-Diamine Sulfate (PTDS) was notably named the American Contact Dermatitis Society Allergen of the Year for 2025 due to its potent allergenicity and common cross-reactivity with p-Phenylenediamine (PPD).

Your Skin

Skin Compatibility

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

Our Assessment

Verdict

Avoid

Toluene-2,5-Diamine is an ingredient with significant sensitization and irritation potential, making it highly unsuitable and actively discouraged for use in precision skincare formulations.

Related

Similar Ingredients

Finding similar ingredients…