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Topical cosmetic ingredient — not a dietary supplement
Cysteamine (topical) is a topical cosmetic ingredient, not a supplement you take internally and not a drug. It is sold legally in skincare products to affect the appearance of skin (such as wrinkles). The evidence below comes mostly from small, often industry-funded studies of topical application, so treat the effect sizes cautiously. This page is for transparency and education, not a recommendation.
What the evidence says
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
ModerateBy outcome
Cysteamine (topical) has an evidence score of 6/10 — moderate evidence based on 7 indexed studies, including 1 meta-analysis. A newer non-hydroquinone skin-lightening cream for melasma — an aminothiol naturally present in cells, applied to the skin. The honest framing: cysteamine 5% has a genuinely respectable evidence base — multiple double-blind placebo-controlled RCTs and a 2024 meta-analysis show it significantly beats placebo for melasma, and several head-to-head trials pit it against hydroquinone and triple-combination creams. But its ceiling is capped: against hydroquinone it is non-superior (and in one direct comparison actually inferior), trials are small and several share a manufacturer-affiliated author, and its main real-world drawback is tolerability — a characteristic sulfur odor plus erythema/burning. A credible, hydroquinone-free alternative, not a clear upgrade. Representative study: PMID 39673630.
Practical, evidence-based guides that cover Cysteamine (topical).
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Last reviewed June 2026 · evidence from 7 studies · how we score
This information is for educational purposes only. It is not a substitute for professional medical advice. Always consult a qualified healthcare provider before starting, stopping, or changing any supplement or medication.
Cysteamine 5% cream (topical depigmenting agent)
A newer non-hydroquinone skin-lightening cream for melasma — an aminothiol naturally present in cells, applied to the skin. The honest framing: cysteamine 5% has a genuinely respectable evidence base — multiple double-blind placebo-controlled RCTs and a 2024 meta-analysis show it significantly beats placebo for melasma, and several head-to-head trials pit it against hydroquinone and triple-combination creams. But its ceiling is capped: against hydroquinone it is non-superior (and in one direct comparison actually inferior), trials are small and several share a manufacturer-affiliated author, and its main real-world drawback is tolerability — a characteristic sulfur odor plus erythema/burning. A credible, hydroquinone-free alternative, not a clear upgrade.
Multiple double-blind placebo-controlled RCTs and a 2024 meta-analysis show cysteamine 5% significantly beats placebo for melasma, with unusual breadth of head-to-head data — but against hydroquinone it is non-superior (and inferior in one direct comparison), trials are small and partly manufacturer-affiliated, and tolerability/odor limit real-world use.
Cysteamine (2-aminoethanethiol) is an aminothiol naturally present in cells (a breakdown product of coenzyme A) used topically at 5% as a non-hydroquinone depigmenting cream for melasma and hyperpigmentation. This entry covers TOPICAL cosmetic use.
Mechanistically it inhibits tyrosinase and key downstream steps of melanin synthesis, acts as an intracellular antioxidant/thiol that diverts pigment-forming intermediates, and chelates the copper/iron involved in melanogenesis.
The clinical evidence is, for a newer agent, unusually solid: two double-blind placebo-controlled RCTs (Mansouri et al., 2015, n=50; Farshi et al., 2018, n=40) both showed significantly lower MASI with cysteamine 5% than placebo over four months, and a 2024 systematic review and meta-analysis of seven RCTs confirmed a significant pooled effect versus placebo (SMD -0.84, I²=0%).
It also has unusual breadth of head-to-head data: against modified Kligman's formula it performed at least as well with better tolerability (Karrabi et al., 2021), and against hydroquinone 4%/ascorbic acid it was equivalent on MASI (Sepaskhah et al., 2022).
The honest counter-evidence caps the score: the meta-analysis found no significant difference versus hydroquinone 4% (non-superiority, not superiority), and the best evaluator-blinded direct comparison (Lima et al., 2020) found cysteamine actually inferior to hydroquinone on mMASI and quality of life.
Trials are small (n=40-65), several share Iranian centers and a manufacturer-affiliated co-author, durations are short (~4 months), and the practical limitations are real: cysteamine has a characteristic unpleasant sulfur/thiol odor and commonly causes erythema and burning.
So the honest summary: topical cysteamine 5% is an evidence-backed, hydroquinone-free option for melasma with a safer long-term profile (no ochronosis), but it is roughly hydroquinone-equivalent at best, with tolerability/odor as the main barrier to adherence. None of this is a health claim.
It is listed under Beauty & Appearance so it is discoverable, but is sandboxed out of ingestible-supplement stacks and the schedule optimizer; it carries a cosmetic badge and a topical-only disclaimer.
Cysteamine inhibits tyrosinase and downstream steps of melanin synthesis, and as an intracellular aminothiol it acts as an antioxidant that diverts pigment-forming intermediates (e.g. dopaquinone) away from melanin. It also chelates the copper/iron involved in melanogenesis.
Unlike hydroquinone, cysteamine is a naturally occurring molecule that is not melanocyte-cytotoxic and is not associated with exogenous ochronosis, which is the basis for positioning it as a safer long-term, hydroquinone-free option.
Topical cosmetic. Cysteamine 5% cream is typically applied once daily to areas of melasma as a short-contact treatment (left on for ~15 minutes, then washed off) to limit odor and irritation, with daily sunscreen. There is no oral or systemic use in this context. This library does not provide an ingestion protocol.
| Form | Type |
|---|---|
| 🧴Cysteamine 5% cream (short-contact application) | Recommended |
| 💊Hydroquinone (more potent but ochronosis risk) or azelaic acid/tranexamic acid for tone | Alternative |
There is no oral or injectable cosmetic form. Cysteamine is applied to the skin surface.
Minimum: 8 weeks
Optimal: 16 weeks
Cycling: Not required
Note: Applied once daily (often short-contact, then rinsed) with daily sunscreen. As a topical there is no ingestion or meal-timing consideration.
Cysteamine 5% is a topical skin-lightening cream for melasma — an alternative to hydroquinone without ochronosis risk. It is a cosmetic active, not an ingested supplement, and does not treat any disease.
Significantly lowers melasma severity versus placebo across double-blind RCTs, comparable to hydroquinone-based regimens in several head-to-head trials.
Meta-analysis shows no significant difference vs hydroquinone 4%, and one evaluator-blinded trial found it inferior. Choose it for the hydroquinone-free/no-ochronosis profile, not for greater potency.
Cysteamine has a characteristic unpleasant sulfur/thiol smell and commonly causes erythema and burning — the main reasons people struggle to stick with it. Short contact times and rinsing help.
Limited data for topical cysteamine in pregnancy; discuss with a clinician (azelaic acid is the better-studied option).
Use short-contact application and build tolerance; erythema/burning are common early.
A reasonable hydroquinone-free alternative with no ochronosis risk, accepting roughly comparable efficacy and the odor/irritation trade-off.
Combining with other irritants can worsen erythema/burning; introduce gradually and use short-contact application. Not a systemic interaction — it is not ingested.
Tip: Use short-contact application (rinse after ~15 min), moisturize, and reduce frequency if needed.
Tip: Short-contact use and rinsing reduce the smell; it is the main adherence barrier.
The commonly studied dose of Cysteamine (topical) is Topical cosmetic. Cysteamine 5% cream is typically applied once daily to areas of melasma as a short-contact treatment (left on for ~15 minutes, then washed off) to limit odor and irritation, with daily sunscreen. There is no oral or systemic use in this context. This library does not provide an ingestion protocol.. Individual needs vary — start at the lower end of the range and adjust based on how you respond.
Timing is flexible for Cysteamine (topical) — consistent daily use matters more than the time of day. Cysteamine cream is a leave-on/short-contact topical with no meal-timing relationship; many protocols use a ~15-minute contact time then rinse to reduce odor and irritation.
Cysteamine (topical) is generally safe at recommended doses, with a few precautions worth noting. The most commonly reported side effects are erythema and burning, unpleasant sulfur/thiol odor. Use caution if any of these apply to you: For topical (skin) use only — not for ingestion, not for injection; Known allergy/sensitivity to cysteamine; Application to broken, irritated, or sunburned skin until healed.