Background  Skin pH may be influenced by various factors, such as hydration of stratum corneum, rate of sebum excretion rate, transepidermal water loss (TEWL) and sweating in relation to skin ageing. Objective  The aim of this study was to evaluate the correlation between skin pH and wrinkle formation that is directly related to ageing. In addition, we investigated the factors related to skin ageing by comparing the association between skin pH and other skin properties. Methods  Three hundred volunteers were selected from three countries: Korea, Vietnam and Singapore. Hydration on the stratum corneum, the rate of sebum excretion rate, melanin index, TEWL and skin temperature on the cheek were measured in a controlled room, and wrinkle length and depth using replicas were compared with skin pH variation. Results  The mean and standard deviation of skin surface pH among the three countries were 5.510 ± 0.625. The greatest gap of skin pH that revealed significant differences for skin properties was represented between the Koreans and the Vietnamese. For all three countries, skin hydration, melanin contents, wrinkle length, wrinkle depth and skin temperature were significantly correlated with skin pH. Factors related to skin moisturizing, such as skin hydration, sebum excretion rate and skin temperature, were negatively correlated with skin pH. Wrinkle length and depth decreased as skin pH became more acidic. Conclusions  Skin properties displayed various values depending on skin pH. In particular, wrinkle formation significantly decreased as skin pH becomes more acidic. We conclude that skin pH is determined by skin properties, such as skin hydration, sebum excretion rate, melanin concentration, TEWL and skin temperature that affects wrinkle formation.

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