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Head-to-head evidence comparison — which supplement is right for you?
Vitamin C (topical) wins 1 of 3 categories. Both are solid choices — the best pick depends on your specific goals.
Verdict
Mostly mechanism / observational
Top outcomes
Verdict
Mostly mechanism / observational
Top outcomes
Shared outcomes (1)
Outcomes where both Cysteamine (topical) and Vitamin C (topical) have evidence — compare verdict strength side-by-side.
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.
any
Cysteamine 5% cream (short-contact application)
Topical cosmetic only. L-ascorbic acid serums are typically 10-20% (often near pH 3 for absorption); stable derivatives are used at varying percentages. Apply a few drops to clean, dry skin, usually in the morning under sunscreen (its antioxidant action complements SPF). There is no oral, injectable, or systemic dose in this cosmetic context. This library does not provide an ingestion protocol.
morning
Leave-on topical serum (10-20% L-ascorbic acid) or a stable vitamin C derivative
Throughout
8-16 weeks
Throughout
Throughout
Throughout
8-12 weeks
8-24 weeks
Throughout
Evaluation of the efficacy of cysteamine 5% cream in the treatment of epidermal melasma: a randomized double-blind placebo-controlled trial.
Br J Dermatol (2015) · Rct · n=50
First double-blind placebo-controlled RCT of cysteamine 5% cream for epidermal melasma (n=50), nightly for 4 months
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.
J Dermatolog Treat (2018) · Rct · n=40
Second double-blind placebo-controlled RCT (n=40), nightly cysteamine 5% for 4 months, with Dermacatch and Mexameter colorimetry
A comparative study of topical 5% cysteamine versus 4% hydroquinone in the treatment of facial melasma in women.
Int J Dermatol (2020) · Rct · n=40
Multicenter evaluator-blinded head-to-head of cysteamine 5% vs hydroquinone 4% (n=40), nightly for 120 days with sunscreen
Use of topical ascorbic acid and its effects on photodamaged skin topography.
Arch Otolaryngol Head Neck Surg (1999) · Rct · n=19
Split-face, randomized, double-blind, vehicle-controlled trial: active L-ascorbic acid serum vs vehicle daily for 3 months in mild-to-moderate facial photodamage
Topical ascorbic acid on photoaged skin. Clinical, topographical and ultrastructural evaluation: double-blind study vs. placebo.
Exp Dermatol (2003) · Rct
6-month double-blind randomized trial comparing 5% vitamin C cream vs its excipient on photoaged skin of the low-neck and arms
Efficacy of topical vitamin C in melasma and photoaging: A systematic review.
J Cosmet Dermatol (2023) · Systematic review
Systematic review of prospective RCTs of topical vitamin C in melasma or photodamage: 7 publications, 139 total volunteers
Vitamin C (topical) has a higher evidence score (6/10 vs 6/10) and wins in 1 of 3 categories.
Both Cysteamine (topical) and Vitamin C (topical) score equally (70) for even skin tone.
No known interactions between Cysteamine (topical) and Vitamin C (topical) have been documented in our database. However, always consult a healthcare provider before combining supplements.