Synopsis

Source of validity: Scientific
Rating (out of 5): 2

L-cystine is a sulfur-containing amino acid and the oxidized dimer form of L-cysteine. Its use in acne treatment is primarily based on its role in the synthesis of keratin and glutathione, both of which are important for skin health. There is some scientific basis—albeit limited—for its inclusion in formulations aimed at reducing acne. L-cystine has been included in combination oral therapies (such as with vitamin B6 or methionine) for acne vulgaris, particularly in Europe. Small clinical studies from the mid-20th century suggested that these combinations may help reduce sebum production and improve skin lesions, possibly due to cystine’s involvement in keratinization and antioxidative pathways. More recent laboratory studies highlight cystine’s role in supporting the skin’s antioxidant defenses, which could theoretically reduce inflammation associated with acne. However, robust, large-scale, contemporary clinical trials evaluating L-cystine as a monotherapy for acne are lacking. Its efficacy remains less substantiated compared to established acne treatments like retinoids, antibiotics, or benzoyl peroxide. In summary, some scientific rationale and early clinical data exist for L-cystine’s use in acne, but the overall quality and quantity of evidence are limited. Therefore, L-cystine may be considered as an adjunct, not a primary, therapy for acne based on current evidence.

More about L-cystine
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Other ingredients used for Acne

Other health conditions supported by L-cystine

Products containing L-cystine

Thorne Amino Complex Berry
Thorne Amino Complex Lemon
Douglas Laboratories Free Form Amino
Klean Athlete Klean Isolate ™