['Photodynamic therapy (PDT) is a highly effective treatment for actinic keratoses (AK); however, it is time consuming and often painful for the patient. Daylight-PDT would make the treatment independent of the clinic and less painful due to the continuous activation of small amounts of porphyrins during its formation.', 'The objective of this randomized controlled study was to compare response rates and adverse effects after methyl aminolevulinate (MAL)-PDT using conventional red light-emitting diode (LED) light vs. daylight.', 'Twenty-nine patients with AK of the face and scalp were treated with MAL-PDT in two symmetrical areas. One area was illuminated by red LED light (37 J cm(-2)) after 3-h incubation with MAL under occlusive dressing. The other area was treated with daylight for 2.5 h after the MAL cream had been under occlusion for half an hour.', 'We found no significant difference in the treatment effect between the two treatments (P = 0.13), with a reduction of AK lesions of 79% in the daylight area compared with 71% in the LED area. Treatment response in the daylight area did not depend on the intensity of the daylight. Illumination with LED was more painful than daylight (P < 0.0001). Erythema and crusting occurred after both treatments and were similar in the two areas.'] Is continuous activation of PpIX by daylight as effective as and less painful than conventional photodynamic therapy for actinic keratoses ; a randomized , controlled , single-blinded study?