Ultraviolet-B (UVB) phototherapy is a well-established mode of treatment for several types of dermatological disease. For psoriasis and vitiligo, narrow band UVB (NB-UVB) phototherapy is an effective therapy, demonstrating greater efficacy and safety compared to broadband UVB or psoralen plus UVA treatments. While the treatment efficacy of NB-UVB artificial light sources is well documented, the long term time and cost commitment of the therapy remains a barrier to treatment adherence. Natural sunlight is an ideal source of accessible UVB radiation; however, exposure to natural sunlight generally results in erythema prior to the accumulation of sufficient dosage of therapeutic wavelengths of UVB. This communication describes a novel topical cream designed to selectively deliver NB-UVB therapy when exposed to sunlight. The topical cream when combined with natural sunlight could offer patients a more convenient phototherapy option for psoriasis and vitiligo, potentially increasing patient compliance.