Tabriz University of Medical Sciences Pharmaceutical Sciences 1735-403X 32 2 2026 04 30 Analyzing Hair Damage Caused by SLS and SLES: Correlation Between Lowry Method and Zein Test 232 242 10.34172/PS.026.42483 EN Sara Sajjadi https://orcid.org/0000-0002-3274-6726 Vahid Abdollahian Farnaz Monajjemzadeh https://orcid.org/0000-0001-9369-5136 Journal Article 10.34172/PS.026.42483 2025 04 09 2025 08 10 Background: This study aimed to investigate the impact of sodium lauryl sulfate (SLS) and sodium lauryl ether sulfate (SLES), two anionic surfactants, on human hair at different pH levels and temperatures, using the Lowry method and Zein tests to assess hair damage and to check the Zein test’s relevance to hair protein loss data. Methods: Hair bundles were placed in solutions of SLS and SLES at varying concentrations (5, 10, 20, and 30% w/v), pH levels (5, 7, and 8), temperatures (37 ℃ and 42 ℃), and durations (10 minutes and 24 hours). Then, the samples were analyzed for absorption at 750 nm using a UV-visible spectrophotometer. The results were compared with the Zein test. Results: With a 10-minute exposure duration, elevating the concentrations of SLS and SLES from 5% to 30% resulted in a threefold increase in protein loss for SLS, compared by a sixfold increase for SLES. While the elevation of pH led to a rise in protein loss for both surfactants, the extent of this increase was more pronounced in SLS than in SLES. An increase of 5 ℃ in temperature during exposure to the surfactants nearly doubled the protein loss. Long exposure time to SLS exhibited minimal impact on the extent of protein loss. In contrast, prolonged exposure to SLES significantly increased protein loss. A good correlation was observed between the results of the Lowry and the Zein tests. Conclusion: The research provided important information on factors like pH, concentration, and exposure time that can impact protein loss results. The findings suggest that hair care products should be formulated with lower concentrations of these surfactants at pH levels of 5-7 to minimize protein loss. Manufacturers can use Zein test and the Lowry method in parallel to evaluate hair damage in a comparative manner.