BACKGROUND Obese subjects frequently show skin diseases. However, less attention has been paid to the impact of obesity on skin disorders until now. OBJECTIVE The purposes of this study are: to highlight the incidence of some dermatoses in obese subjects and to study the water barrier function of the obese skin using transepidermal water loss (TEWL). METHODS Sixty obese subjects and 20 normal weight volunteers were recruited. Obese group was further divided into three body mass index (BMI) classes: class I (BMI 30-34.9 kg/m(2)), class II (BMI 35-39.9 kg/m(2)) and class III (BMI 40 g/m(2)). All subjects attended dermatological examination for skin diseases. To assess barrier function, TEWL measurements were performed on the volar surface of the forearm using a tewameter. RESULTS The results of this study showed that: (i) obese subjects show a higher incidence of some dermatoses compared with normal-weight controls; in addition the dermatoses are more, frequent as BMI increases; (ii) the rate of TEWL is lower in obese subjects, than in the normal-weight subjects, particularly in patients with intra-abdominal obesity. CONCLUSIONS Specific dermatoses as skin tags, striae distensae and plantar hyperkeratosis, could be considered as a cutaneous stigma of severe obesity. The low permeability of the skin to evaporative water loss is observed in obese subjects compared with normal weight control. Although the physiological mechanisms are still unknown, this finding has not been previously described and we believe that this may constitute a new field in the research on obesity.