Photodynamic therapy was invented around 1900. PDT requires the interaction between a photo-senitizer, oxygen, and light. Several photosensitizers are being developed. The most commonly used photosensitizer for NMSC is aminolevulenic acid. The concept of photodynamic therapy (PDT) was developed more than 100 years ago in Germany by the medical student Oscar Raab and Professor Herman von Tappeiner in Munich, studying the effects of acri-dine and light on malaria-causing protozoa . In the space of a few years the idea was developed and logical conclusions about the mechanisms drawn, which have since proved to be accurate. In the first therapeutic application of the new method, von Tappeiner and Jesionek used a combination of topical eosin and white light to treat skin tumors . The method was then only slowly developed until the late 1970s when a resurgence of interest was noted following the paper by Dougherty reporting a large series of patients treated with PDT . Twenty-five patients with 113 primary or secondary skin tumors (both BCC and SCC) were studied, and of these only two were resistant to PDT. Since then a number of studies have reported beneficial effects of PDT in skin cancer, esophageal and non-small-cell lung cancer, bladder cancer, as well as several other non-neoplastic diseases. The treatment is now routinely being used for both superficial skin cancer and actinic keratoses.