New strategies to improve skin barrier homeostasis.

The uppermost thin layer, stratum corneum, plays a crucial role as a water impermeable barrier. After acute damage, it recovers automatically, but with aging or psychological stress, the recovery is delayed. Frequent damage, or damage under a dry environment, induces epidermal hyperplasia or inflammation. A specific protease inhibitor, histamine antagonist, and some magnesium salts have been demonstrated to accelerate the barrier recovery. These treatments also mitigated the epidermal hyperplasia induced by repeated barrier disruption or the damage under a dry condition. For the delay of the barrier repair induced by psychological stress, a glucocorticoid receptor antagonist or reduction of the stress by some specific odorant was significantly effective. Recently, the ion flux in the epidermis was found to be crucial for the barrier homeostasis. An external negative electric field accelerated the skin barrier recovery. These new methods to improve skin barrier homeostasis could be useful strategies to solve skin problems.