Continuous ultra-low-intensity artificial daylight is not as effective as red LED light in photodynamic therapy of multiple actinic keratoses

Daylight-mediated photodynamic therapy (PDT) is a simple and tolerable treatment of nonmelanoma skin cancer. It is of interest which light intensity is sufficient to prevent accumulation of protoporphyrin IX (PpIX) and effectively treat actinic keratoses (AKs). We compared the efficacy of PDT with light-emitting diode (LED) to daylight-mediated PDT with very low-intensity artificial daylight ('daylight') in the treatment of multiple AKs in the face or scalp.