Clinical dermatology • Original article CED Clinical and Experimental Dermatology New topical photodynamic therapy for treatment of hidradenitis suppurativa using methylene blue niosomal gel: a single-blind, randomized, comparative study M. A. Fadel 1 and A. A. Tawfik 2 1 Drug Delivery and Nanotechnology Unit; and 2 Dermatology Unit, Department of Medical Applications of Lasers (MAL), National Institute of Laser Enhanced Sciences (NILES), Cairo University, Cairo, Egypt doi:10.1111/ced.12459 Summary Background. Hidradenitis suppurativa (HS), is a chronic, recurrent dermatosis affecting skin that contains apocrine glands. Photodynamic therapy using amino- laevulinic acid (ALA) activated by intense pulsed light (IPL) have shown variable success rates, with some adverse effects. Aims. To evaluate the efficacy and safety of methylene blue (MB) as a photosensi- tizer delivered as a niosomal gel for the treatment of HS using IPL. Methods. We enrolled 11 patients with HS in the study, which was a randomized split-body study. One side of each patient’s body was treated with niosomal MB (NMB) gel and the other side was treated with unloaded (free) MB (FMB) gel. The affected sites were irradiated using IPL with a 630 nm filter. Patients were followed up at 1, 3 and 6 months after treatment. Results. Drug release from the FMB gel was significantly higher (P > 0.05) than from the NMB gel. Lesions showed 77.3% and 44.1% reduction on the NMB and FMB sides, respectively. A significant reduction in the Hidradenitis Suppurativa Lesion, Area and Severity Index (HS-LASI) after treatment was elicited in both groups, with no pain, erythema or hyperpigmentation. Conclusion. The combination of MB as a photosensitizer activated with 630 nm IPL as a light source is a successful PDT for HS. Delivery of MB in niosomes was more effective for drug penetration to the dermis compared with delivery by FMB gel. The 630 nm filter was not only a source of activation of MB but also a means of hair-follicle destruction. Introduction Hidradenitis suppurativa (HS) is a chronic, recurrent dermatosis affecting skin that contains apocrine glands, such as the axillae, perineum and infra- mammary regions. 1 The pathogenesis of HS is believed to involve the hair follicles. It is thought that the hair follicle becomes occluded at the level of the apocrine gland and ruptures, which initiates an inflammatory response. 2,3 Previous treatments have included long- term antibiotics, antiandrogens, tumour necrosis factor and surgery. 4,5 Nd-YAG (neodymium-doped–yttrium– aluminum–garnet) laser has been used successfully for HS treatment by targeting hair follicles. 3 Previous studies using aminolaevulinic acid (ALA) as a photosensitizer have shown variable success rates in treatment of HS, 6–8 with differences in the success rate in these studies being attributed to insufficient penetra- tion of the photosensitizer. 8 Moreover, a number of adverse effects have been encountered with ALA photodynamic therapy (PDT), including discomfort, Correspondence: Dr Abeer A. Tawfik, Dermatology Unit, Department of Medical Applications of Lasers (MAL), National Institute of Laser Enhanced Sciences (NILES), Cairo University, Cairo, Giza 12316, Egypt E-mail: dr.abeertawfik@gmail.com Conflict of interest: the authors declare that they have no conflicts of interest. Accepted for publication 5 March 2014 Clinical and Experimental Dermatology 1 ª 2014 British Association of Dermatologists