Cysteamine and melasma

Most subjects covered in this column are botanical ingredients used for multiple conditions in topical skin care. The focus this month, though, is a natural agent garnering attention primarily for one indication. Present in many mammals and in various cells in the human body (and particularly highly concentrated in human milk), cysteamine is a stable aminothiol that acts as an antioxidant as a result of the degradation of coenzyme A and is known to play a protective function.¹ Melasma, an acquired recurrent, chronic hyperpigmentary disorder, continues to be a treatment challenge and is often psychologically troublesome for those affected, approximately 90% of whom are women.² Individuals with Fitzpatrick skin types IV and V who reside in regions where UV exposure is likely are particularly prominent among those with melasma.² While triple combination therapy (also known as Kligman’s formula) continues to be the modern gold standard of care for melasma (over the last 30 years),³ cysteamine, a nonmelanocytotoxic molecule, is considered viable for long-term use and safer than the long-time skin-lightening gold standard over several decades, hydroquinone (HQ), which is associated with safety concerns.⁴ This month’s column is a review of recent findings on the efficacy and safety of cysteamine for the treatment of melasma.

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Recent history and the 2015 study

Prior to 2015, the quick oxidation and malodorous nature of cysteamine rendered it unsuitable for use as a topical agent. However, stabilization efforts resulted in a product that first began to show efficacy that year.⁵

Mansouri et al. conducted a randomized, double-blind, placebo-controlled trial to assess the efficacy of topical cysteamine 5% to treat epidermal melasma in 2015. Over 4 months, 50 volunteers (25 in each group) applied either cysteamine cream or placebo on lesions once nightly. The mean differences at baseline between pigmented and normal skin were 75.2 ± 37 in the cysteamine group and 68.9 ± 31 in the placebo group. Statistically significant differences between the groups were identified at the 2- and 4-month points. At 2 months, the mean differences were 39.7 ± 16.6 in the cysteamine group and 63.8 ± 28.6 in the placebo group; at 4 months, the respective differences were 26.2 ± 16 and 60.7 ± 27.3. Melasma area severity index (MASI) scores were significantly lower in the cysteamine group compared with the placebo group at the end of the study, and investigator global assessment scores and patient questionnaire results revealed substantial comparative efficacy of cysteamine cream.⁶ Topical cysteamine has also demonstrated notable efficacy in treating senile lentigines, which typically do not respond to topical depigmenting products.⁵

Farshi et al. used Dermacatch as a novel measurement tool to ascertain the efficacy of cysteamine cream for treating epidermal melasma in a 2018 report of a randomized, double-blind, placebo-controlled study with 40 patients. During the 4-month trial, cysteamine cream or placebo was applied nightly before sleep. Investigators measured treatment efficacy through Dermacatch, and Mexameter skin colorimetry, MASI scores, investigator global assessments, and patient questionnaires at baseline, 2 months, and 4 months. Through all measurement methods, cysteamine was found to reduce melanin content of melasma lesions, with Dermacatch performing reliably and comparably to Mexameter.⁷ Since then, cysteamine has been compared to several first-line melasma therapies.