[Mechanisms of phototherapy].

Phototherapy represents one of the essential options in the treatment of skin diseases by dermatologists. The beginnings of phototherapy were based on empirical observations and only later the underlying molecular and cellular mechanisms of the different modalities of phototherapy were unravelled by scientific research. Due to these findings, some phototherapeutic indications were subsequently altered. In this article, the known photobiological effects of ultraviolet radiation will be discussed and put in relation to the different forms of phototherapy as they are applied in the daily practice by dermatologists.