Internal environment of footwear is a risk factor for tinea pedis.

The relation between tinea pedis and the internal environment of footwear has not been scientifically proven. This study aimed to determine whether the internal environment of footwear affects the incidence of tinea pedis and tinea unguium. This cross-sectional, observatory study involved 420 outpatients who were categorized into non-tinea, tinea pedis or tinea unguium groups based on mycological analysis. External climatic conditions, and temperature, humidity and dew points inside the patients' footwear were recorded. Univariate and multivariate analyses were used to determine independent risk factors for tinea pedis and tinea unguium. A significant correlation was found between high temperature/high humidity and dew point of the internal environment of the footwear and the season. Furthermore, those who wore footwear with internal environments characterized by high temperature, high humidity, high-temperature/high-humidity and high dew point values had a significantly higher incidence of tinea pedis. The internal dew point correlated with the incidence of tinea pedis, whereas the external temperature correlated with the incidence of tinea unguium. The internal humidity and dew point of footwear as well as the frequency with which footwear with a high-temperature/high-humidity internal environment were worn was significantly higher in men than in women. In conclusion, the internal environment of footwear is a risk factor for tinea pedis, and this environment is affected by the season. Moreover, the frequency of tinea pedis among men is related to the internal environment of footwear. The dew point is an appropriate index for evaluating temperature and humidity in relation to tinea pedis.