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Cys6.0

Cysteamine (topical) Research

Mostly mechanism / observationalModerate safety

7 peer-reviewed studies

What the evidence says

Mostly mechanism / observational

Most Cysteamine (topical) studies are mechanism or observational rather than RCTs that measure a clinical effect — keep findings provisional.

Most evidence is from mixed-quality meta-analyses and randomised trials published 2015–2024 with a typical study size of 50 participants.

Based on 7 studies · 1 meta-analysis · 5 RCTs · 245 total participants

Confidence

Moderate

By outcome

Skin tone & pigmentationSignificant reduction in melasma vs placebo; a hydroquinone-free alternative (roughly HQ-equivalent at best) · 8-16 weeks
Mostly mechanism / observational6 studies
Safety profile
Too few graded studies2 studies

Active research area

4 studies in the last 5 years · Latest meta-analysis: 2024

20152024

1Meta-Analysis2024

Cysteamine 5% was more effective than placebo in reducing the Melasma Area and Severity Index (SMD - 0.84; 95% CI - 1.19, - 0.49, p < 0.00001, I2 = 0%), but showed no significant difference when compared with hydroquinone 4% (SMD 0.16; 95% CI - 0.22, 0.53, p = 0.42).

Mawu FO, Christopher PM. · Arch Dermatol Res (2024)

RCT-only meta-analysis of 7 trials comparing cysteamine 5% with placebo or hydroquinone
Significantly more effective than placebo (SMD -0.84, I²=0%), but no significant difference vs hydroquinone 4% (non-superiority)
Adverse events higher than placebo but similar to hydroquinone — a comparable, not superior, alternative

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2RCTn=50 · small study2015

At the end of the treatment, the MASI scores were significantly lower in the cysteamine group vs. placebo (7.2 ± 5.5 vs. 11.6 ± 7.9, P = 0.02).

Mansouri P, Farshi S, Hashemi Z, Kasraee B. · Br J Dermatol (2015)

First double-blind placebo-controlled RCT of cysteamine 5% cream for epidermal melasma (n=50), nightly for 4 months
MASI significantly lower with cysteamine than placebo at 4 months (P=0.02), with significant Mexameter differences at 2 and 4 months
Investigator and patient assessments also favored cysteamine — proof-of-concept efficacy

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3RCTn=40 · small study2018

At the end of the treatment period, MASI scores were significantly lower in the cysteamine group versus placebo (8.03 ± 5.2 vs. 12.2 ± 7.4, p = .04).

Farshi S, Mansouri P, Kasraee B. · J Dermatolog Treat (2018)

Second double-blind placebo-controlled RCT (n=40), nightly cysteamine 5% for 4 months, with Dermacatch and Mexameter colorimetry
MASI significantly lower with cysteamine than placebo at 4 months (p=0.04), with significant colorimetric differences at 2 and 4 months
Replicates the 2015 placebo-controlled result with an added objective measure

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4RCTn=40 · small study2020

Cysteamine proved to be safe, well-tolerated, and effective, despite its inferior performance to hydroquinone in decreasing mMASI and MELASQoL in the treatment of melasma.

Lima PB, Dias JAF, Cassiano D, Esposito ACC, Bagatin E, Miot LDB, Miot HA. · Int J Dermatol (2020)

Multicenter evaluator-blinded head-to-head of cysteamine 5% vs hydroquinone 4% (n=40), nightly for 120 days with sunscreen
Hydroquinone outperformed cysteamine on mMASI (53% vs 38% reduction, P=0.017) and on quality of life
Erythema and burning were the most notable cysteamine adverse effects — the key counter-evidence (cysteamine inferior to HQ)

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5RCTn=50 · small study2021

Cysteamine 5% cream showed greater efficacy as compared to MKF... with the advantage of being significantly better tolerated.

Karrabi M, David J, Sahebkar M. · Skin Res Technol (2021)

Double-blind RCT (n=50) comparing cysteamine 5% with modified Kligman's formula (hydroquinone + retinoic acid + betamethasone) over 4 months
mMASI reduction was ~9% greater with cysteamine than MKF (P=0.005, P=0.001)
Cysteamine was also significantly better tolerated than the triple-combination — a favorable head-to-head

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6RCTn=65 · small study2022

Cysteamine was confirmed to be an effective treatment for melasma, with equivalent results to HC in reducing mMASI score and improving quality of life, despite lesser melanin index reduction observed.

Sepaskhah M, Karimi F, Bagheri Z, Kasraee B. · J Cosmet Dermatol (2022)

Single-blind RCT (n=65 completers) comparing cysteamine 5% vs hydroquinone 4%/ascorbic acid 3% over 4 months
Both significantly reduced mMASI with no significant between-group difference
But the hydroquinone combination produced a significantly greater melanin-index reduction (p=0.002)

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7In Vitro2021

L-cysteinamide at certain concentrations can inhibit eumelanin synthesis through a dual mechanism by inhibiting TYR-catalyzed dopaquinone synthesis and by diverting the synthesized dopaquinone to the formation of DOPA-cysteinamide conjugates rather than dopachrome.

Lee HK, Ha JW, Hwang YJ, Boo YC. · Antioxidants (Basel) (2021)

In-vitro study comparing thiol compounds (including cysteamine) against tyrosinase-mediated dopachrome formation and melanin in melanoma cells/melanocytes
Demonstrates the shared aminothiol mechanism: inhibiting tyrosinase-catalyzed dopaquinone synthesis plus diverting dopaquinone into thiol conjugates, lowering total melanin
Supports the mechanistic class (cysteamine tested as a thiol comparator); in-vitro only

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View in Research Library

Cysteamine (topical) Research

Mostly mechanism / observational

Efficacy and safety of cysteamine 5% cream for the management of melasma: a systematic review and meta-analysis of randomized controlled trials.

Evaluation of the efficacy of cysteamine 5% cream in the treatment of epidermal melasma: a randomized double-blind placebo-controlled trial.

Efficacy of cysteamine cream in the treatment of epidermal melasma, evaluating by Dermacatch as a new measurement method: a randomized double blind placebo controlled study.

A comparative study of topical 5% cysteamine versus 4% hydroquinone in the treatment of facial melasma in women.

Clinical evaluation of efficacy, safety and tolerability of cysteamine 5% cream in comparison with modified Kligman's formula in subjects with epidermal melasma: A randomized, double-blind clinical trial study.

Comparison of the efficacy of cysteamine 5% cream and hydroquinone 4%/ascorbic acid 3% combination cream in the treatment of epidermal melasma.

Identification of L-Cysteinamide as a Potent Inhibitor of Tyrosinase-Mediated Dopachrome Formation and Eumelanin Synthesis.