Regional and seasonal differences in skin irritation and neurosensitivity in Chinese and South Korean women.

Background: China has a great variety of geographical and climatic conditions, and several cultural differences exist within the country; thus, understanding the regional and seasonal differences that cause skin sensitivities in this country is important.
Objective: The aim of this study was to assess skin sensitivity of women from six cities in China and from South Korea during the winter and summer seasons to aid the development of suitable and effective dermatological products.
Methods: This multicentre study included 754 healthy female volunteers, and was conducted in the winter (between January and March) and summer (between June and July) of 2011. Patch tests were performed using 0.5% sodium lauryl sulphate (SLS) aqueous solution and 0.15% retinol in 1,3-butylene glycol on the back of the volunteers. Simultaneously, stinging tests were performed on their cheeks by using 5% lactic acid solution and 0.001% capsaicin solution, each in a negative control vehicle (distilled water and 10% ethanol solution, respectively).
Results: The patch test results showed that the subjects in Beijing and Shenyang were more sensitive to SLS, retinol and lactic acid in the winter than were those in Guangzhou, Shanghai, Wuhan, Chengdu and South Korea. The stinging test results revealed that the subjects in Beijing were more neurosensitive to lactic acid in the winter; however, during the same season, the subjects from Shanghai and Guangzhou were significantly more neurosensitive to capsaicin.
Conclusion: Our observations indicate that skin sensitivity differs considerably between women from different parts of China and South Korea. We recommend that these differences be considered during the development of cosmetic products in these countries.
(© 2014 European Academy of Dermatology and Venereology.)