Topical cannabidiol (CBD) in skin pathology – A comprehensive review and prospects for new therapeutic opportunities
Data supporting the findings of this study are available from the corresponding author, L.M., on request.
Humans have utilised cannabis products in various forms throughout the recorded history. To date, more than 500 biologically active components have been identified in the plants of the Cannabis genus, amongst which more than 100 were classified as phytocannabinoids (exocannabinoids). The plant genus Cannabis is a member of the plant family Cannabaceae, and there are three primary cannabis species which vary in their biochemical constituents: Cannabis sativa, Cannabis indica and Cannabis ruderalis. There has been a growing level of interest in research on the topical usage of a cannabis-based extract as a safer and more effective alternative to the usage of topical corticosteroids in treating some dermatoses. Together with the discovery of the cannabinoid receptors on the skin, it has been further illustrated that topical cannabis has anti-inflammatory, anti-itching, analgesics, wound healing and anti-proliferative effects on the skin.
Cannabinoids work on the endocannabinoid system (ECS), which consists of a series of neuromodulatory lipids and receptors located throughout the brain and the central and peripheral nervous system, which accept endogenous cannabinoids (anandamide, 2-arachidonoylglycerol) and phytocannabinoids (plant-based). 1
The (cannabinoid-1) CB1 and (cannabinoid-2) CB2 receptors are two main receptors within the ECS. The two most well-researched phytocannabinoids are the delta-9 tetrahydrocannabinol (THC) and cannabidiol (CBD). Tetrahydrocannabinol is the primary psychoactive component of cannabis which is responsible for the ‘high’ associated with cannabis use. 2
In general, cannabis that has high levels of the psychoactive cannabinoid, delta9-tetrahydrocannabinol (9-THC), and low levels of the non/antipsychoactive cannabinoid, CBD, is referred to as ‘marijuana’. Cannabis that has high levels of CBD, and very low insignificant levels of 9-THC, is referred to as ‘industrial hemp’, or ‘hemp’, and has no psychoactive effects. 3,4
Elements of the ECS were extensively documented in epidermal keratinocytes, melanocytes, mast cells and cutaneous immune regulatory system. Moreover, cannabinoids were shown to suppress in vitro proliferation (and differentiation) of cultured epidermal keratinocytes, alter pain and stimulate wound healing, and have anti-microbial and pruritic properties. 5,6
Substances penetrate the outer layer of the skin and permeate from one layer to another. Substances are transferred through the main barrier of the skin, the stratum corneum, by passive diffusion into the underlying viable layers of the epidermis. 7
Uptake of a substance is proportional to compound’s concentration gradient between the formulation and the base of the stratum corneum. The extent of the uptake varies widely with the physicochemical properties of the xenobiotic, the formulation and application of the product, and with skin conditions. 7,8
There is always a need to seek more clinically efficient, safer and widely available methods of treating medical conditions, skin pathology is no different. Even more interesting, topical use of cannabis as a form of treatment covers a wider scope of skin disorders as highlighted in the discussion.
The purpose of this review article is to look broadly at the medicinal benefits of cannabis in treating a variety of skin disorders. It is a succinct summary of current knowledge based on a meta-analysis of global literature on the subject matter. As such, no article was excluded when literature was gathered; this was with a deliberate aim of excluding bias, promoting a fair, balanced and comprehensive evidence-based article.
Cannabinol-based studies promise to be a key feature in literature and might lead to a breakthrough that will add a different dimension to how we see skin pathology treatment for a plethora of skin diseases (see Figure 1 ).