Background: Existing topical psoriasis treatments are partially effective or have long-term side effects for a proportion of people with psoriasis; therefore, effective and safe treatment options are required. Cannabidiol, a cannabinoid in Cannabis sativa, reverses the etiology of psoriasis through skin receptors according to in vitro research. Cannabidiol transdermal patches may be an effective treatment for psoriasis, although the efficacy and safety data are limited. Methods and analysis: This is a randomized double-blind controlled trial comparing cannabidiol (CBD) with minimal tetrahydrocannabinol (THC) patches with placebo patches (1:1 ratio) daily applied to comparable lesions of each patient with mild to moderate plaque-type psoriasis performed in a university hospital in Thailand (n=60). The primary outcome is the local psoriasis severity index (LPSI). The local severity index of psoriasis, the itch score using the visual analog scale, and adverse events will be evaluated on day 0, 30, 60, and 90 of the study. Furthermore, on days 0 and 90 of this study, biological samples will be taken for the evaluation of the skin, gut, and mouth microbial profile of 50% of randomly selected individuals. Conclusions: This study aims to investigate the efficacy and safety of cannabidiol transdermal patches in alleviating the symptoms of psoriasis. We will also examine personal impacts on the efficacy and safety of patches, such as the microbial profile. The results of this study may highlight a novel topical treatment option that reduces suffering in patients with psoriasis. Ethics and dissemination: This study was registered with the Thai Clinical Trials Registry (TCTR No. 20220518004). The protocol is being considered by the Institutional Review Board of the Faculty of Medicine, Chulalongkorn University. The results of this study will be faithfully presented through conferences or published articles.

Following the discovery of various effects on skin function by modifying endocannabinoid systems, multiple preclinical studies have revealed the promise of cannabis and cannabinoids in the treatment of a variety of skin diseases. However, its clinical efficacy is still debated. This systematic review aims to evaluate the therapeutic efficacy of cannabis and cannabinoids in dermatological conditions and diseases. The protocol has been prepared using the Preferred Items for Systematic Review and Meta-analysis Protocols (PRISMA-P) guidelines and has been registered with the International Prospective Register of Systematic Reviews (PROSPERO: CRD42023397189). PubMed, EMBASE, SCOPUS, Cochrane Central Register of Controlled Trials (CENTRAL), and Web of Science will be used for the systemic search. The outcomes will be an improvement in dermatological characteristics, including disease-specific composite scores and objective and subjective outcomes of skin conditions. This systematic review will provide valuable information on dermatological therapy of cannabis and cannabinoids and could be the start of future research and medicinal applications.

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