Transepidermal water loss (TEWL) and water content of the stratum corneum, when measured simultaneously, provide important information regarding skin function. On the basis of the model presented, it is possible to differentiate dry senile skin from dry pathological skin (such as psoriasis, atopic dermatitis, irritant reaction), clinically involved or uninvolved. Pathological dry skin, because of the impaired barrier function is associated with increased TEWL and low corneum water content. Senile skin, on the other hand, shows both, decreased TEWL and stratum corneum water content. It is suggested that with this model it may be possible to differentiate uninvolved pathologic from healthy skin.