Noninvasive test methods for epidermal barrier function.

New bioengineering techniques provide noninvasive opportunities to evaluate clinically the application of various products on the skin. The skin barrier function and its integrity can be studied by transepidermal water loss, stratum corneum water content, transcutaneous flux of carbon dioxide and oxygen, and transepidermal movement of ions, particularly chloride, potassium, and hydrogen ions. The benefits of noninvasive techniques are due not only to their lack of skin barrier destruction but also to their potential for early detection of any subclinical effects not detected by the naked eyes.