Meteorology and ethnicity as critical factors in HRIPT: Comparing responses between Chinese and Indian ethnicities.

BACKGROUND: Human repeated insult patch test (HRIPT) is regarded as one of the confirmatory test in determining the safety of skin sensitizers. A number of important factors should be considered when conducting and interpreting the results of the HRIPT. OBJECTIVE: To investigate for probable critical factors that influence the results of HRIPT with the same protocol in Shanghai and Mumbai. METHODS: Two HRIPTs were carried out in Shanghai and Mumbai in 2011. Six identical products and 1% sodium lauryl sulfate were tested. Two Chinese dermatologists performed the grading in the two cities. Climate conditions of Shanghai and Mumbai were also recorded. RESULTS: For four lower reaction ratio products, cumulative irritation scores in the induction phase were higher in individuals whose ethnicity was Indian rather than Chinese. Reaction ratio of the same four products was highly correlated to the climatic parameters. The other two higher reaction ratio products and the positive control had no difference between the two ethnicities. CONCLUSION: Greater attention ought to be paid to the impact of climate on the results of HRIPT, especially for the mild irritation cosmetics when giving the interpretation. Greater emphasis also needs to be placed on the ethnicity of the subjects.