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Moumoujus

RHODODENDROL.

Avoid CAS 69617-84-1 / SKIN CONDITIONING

Rhododendrol is a potent tyrosinase inhibitor designed to reduce melanin production. However, its metabolism within the skin generates highly reactive, cytotoxic products that lead to irreversible melanocyte destruction and severe depigmentation, prompting its global withdrawal from cosmetic markets.

Summary

skin brightening tyrosinase inhibitor

Science

Mechanism of Action

Rhododendrol functions by competitively inhibiting tyrosinase, a key enzyme in melanin synthesis. Critically, it also acts as a substrate for tyrosinase, metabolizing into cytotoxic products such as RD-quinone. These reactive species induce melanocyte death through various pathways, including binding to sulfhydryl proteins (leading to ER stress), generating pro-oxidant rhododendrol-derived melanins (causing oxidative stress), and impairing melanocyte proliferation via ROS-dependent GADD45 activation. UV exposure has been shown to exacerbate its cytotoxicity.

Research

Clinical Evidence

High confidence
Effective range N/A
Optimal

N/A

Key findings

  1. 01 Clinical reports and epidemiological surveys in Japan identified a higher frequency of leukoderma in individuals using cosmetics with 2% rhododendrol, leading to product withdrawal.
  2. 02 A patch test with 2% rhododendrol in petrolatum resulted in a positive reaction in 13.5% (25/185) of tested patients.
  3. 03 Daily application of 30% rhododendrol in hk14-SCF transgenic hairless mice induced depigmentation and melanocyte loss within 14 days.

Transparency

Dusting Analysis

Not commonly dusted
Red flag below
2%

Rhododendrol was deliberately used as an active ingredient for skin lightening. However, concentrations as low as 2% were directly linked to widespread chemical depigmentation (leukoderma), leading to its market withdrawal. Its primary hazard is severe melanocyte cytotoxicity, rather than simply being ineffective at low doses.

The Formula

Formulation

Solubility
Both
Optimal pH N/A
0 7 14

Stability

Rhododendrol is heat-sensitive, requiring storage below 0°C. Its oxidation product, RD-quinone, is highly unstable, undergoing further unstable conversions, particularly rapidly at acidic pH (below pH 1).

Conflicts

  • UV light (increases cytotoxicity)
  • Low pH (causes RD-quinone instability)

Safety

Safety Profile

CIR Status
Not reviewed
Sensitization risk High

Rhododendrol was withdrawn from the market in 2013 due to widespread reports of inducing leukoderma (chemical depigmentation), even at concentrations of 2%. Its main hazard is severe melanocyte cytotoxicity. No official 'safe as used' status has been established by regulatory bodies; instead, its use led directly to severe adverse effects and product withdrawal.

Your Skin

Skin Compatibility

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

Our Assessment

Verdict

Avoid

Despite its tyrosinase inhibiting properties, rhododendrol's severe and widespread melanocyte cytotoxicity, leading to permanent depigmentation, makes it an ingredient to unequivocally avoid in skincare formulations.

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