Cysteine peptide (Ac-RFAACAA-COOH) is used in combination with Lysine peptide (Ac-RFAAKAA-COOH) in the Direct Peptide Reactivity Assay (DPRA) test. Direct Peptide Reactivity Assay is used in cosmetic applications for the characterization of the skin sensitizing potential of a substance, framed by OECD Guideline no 442.
Cho SA, Jeong YH, Kim JH, Kim S, Cho JC, Heo Y, Suh KD, Shin K, An S. Method for detecting the reactivity of chemicals towards peptides as an alternative test method for assessing skin sensitization potential. Toxicol Lett. 2014 Feb 10;225(1):185-91. doi: 10.1016/j.toxlet.2013.12.007. Epub 2013 Dec 19. Erratum in: Toxicol Lett. 2014 Apr 7;226(1):106. Heo, Young [corrected to Heo, Yong]. PMID: 24362008.