Eczematic dermatoses
Atopic dermatitis
In a small pilot study on pediatric atopic dermatitis in 2007, Pulvirenti et al. evaluated the safety and efficacy of the twice-daily application of a topical emulsion containing a synthetic aliamide (adelmidrol 2%), comparable to its parent substance PEA, in the treatment of 11 males and 9 females with atopic dermatitis (AD), whose mean age was 8 years. Among the 20 pediatric patients, 16 experienced complete resolution of symptoms after 4 weeks of treatment and had no relapses at the 8-week follow-up assessment. No improvement was noted in the six patches of AD in six patients with several untreated lesions that served as controls.15 Also in 2007, Del Rosso reported on a trial in which a PEA-containing nonsteroidal cream significantly lowered the mean time between flares in pediatric and adult AD patients.16
One year later, Eberlein et al. evaluated an emollient containing PEA in AD patients, finding that itch severity and sleep loss were improved by an average of 60%, with 38% of participants stopping oral antihistamines, 33.6% discontinuing topical steroid regimens, and 20% ending their use of topical immunomodulators as the study concluded.4,17
In 2018, Río et al. suggested that targeted manipulation of the endocannabinoid system at various AD stages might rein in the inflammatory and immune responses and ensuing alterations in keratinocytes, thus helping to preserve epidermal barrier function.18 As Trusler et al. noted, though, no control groups were used in the latter two studies, so it is unknown what effect the application of the vehicle alone would have had on the pruritus in these patients.19
Allergic contact dermatitis
In 2007, Karsak et al. demonstrated that mice lacking CB1/2 receptors exhibited aggravated contact hypersensitivity, whereas mice with higher levels of AEA evinced lower cutaneous allergic responses.20
Recently, Petrosino et al. provided the first evidence that the nonpsychotropic cannabinoid cannabidiol conferred anti-inflammatory activity in an experimental in vitro model of allergic contact dermatitis.21
Dermatomyositis
Robinson et al. have found that treating blood samples of patients with dermatomyositis with the nonpsychoactive cannabinoid ajulemic acid appears to limit the production of pathogenic cytokines. They suggest that oral administration of this cannabinoid merits consideration for dermatomyositis.22
Skin cancer
In 2015, Glodde et al. used a mouse model to investigate the role of cannabinoids in skin cancer pathogenesis. They considered THC, which binds to CB1 and CB2, and the endogenous cannabinoid system. The researchers found that in a CB receptor-dependent fashion THC significantly hindered the tumor growth of HCmel12 melanomas in vivo, verifying the merit of exogenous cannabinoids in melanoma treatment. They did not identify a role of the endogenous cannabinoid system in skin cancer pathogenesis.23
Additional studies suggest that endocannabinoids, phytocannabinoids, and synthetic cannabinoids diminish skin cancer growth (melanoma and nonmelanoma) in vitro and in vivo through CB receptor-dependent and -independent pathways, though in vivo human studies have not yet been conducted.8,24