Medical cannabis has now been legalised in a large number of countries around the world, including 19 in Europe alone. The plant and its derivatives are used medicinally in the treatment of a number of conditions, with the most recognised being intractable childhood epilepsy. Extracts of cannabis are also being increasingly studied and utilised for their potential in the treatment of skin conditions such as acne, itching (pruritus), psoriasis, and atopic dermatitis.
The medicinal properties of the cannabis plant are largely owed to the cannabinoids that are found within. These cannabinoids – tetrahydrocannabinol (THC) and cannabidiol (CBD) being the most abundant – have demonstrated a number of valuable medicinal properties. Cannabinoids are believed to have potential roles in the treatment of a variety of conditions due to their interaction with our own Endocannabinoid System (ECS).
The ECS is a system of receptors and neurotransmitters (endocannabinoids) that are expressed throughout our immune system and central nervous system. However, these endocannabinoid receptors have also been found to be expressed in the skin, making cannabinoids an interesting theme of research for the future treatments of skin conditions. In a recent review, published in the Journal of Dermatological Treatment, researchers aimed to review the current evidence available in this area.
What did the research say?
Atopic and Allergic Contact Dermatitis and Cannabinoids
The anti-inflammatory and anti-pruritic properties of cannabinoids may play a role in the management of atopic and allergic contact dermatitis. Past studies have revealed that the manipulation of CB2 receptors in the skin has the potential to both escalate and inhibit inflammatory responses in allergic contact dermatitis.
One study assessed in the review found that topical application of THC reduced inflammation associated with allergic contact dermatitis in mice. In the same study, researchers discovered that subcutaneous (under the skin) application of a CB2 receptor antagonist increased inflammation. The findings of this study were puzzling but perhaps suggest that CB2 antagonism may be initially beneficial to the treatment of dermatitis. However, chronic blockade of the CB2 receptor could, in fact, enhance inflammation.
Other studies also found that the topical application of THC reduced inflammation associated with allergic contact dermatitis. In addition, other CB1-specific agonists were found to significantly reduce skinfold thickness and enhance epidermal permeability barrier function.
The authors of the review concluded that the endocannabinoid system plays a multifactorial role in the inflammatory response associated with atopic dermatitis with further studies required to detail the clinical effects within the target population.
Pruritis (itch) and Cannabinoids
Pruritus has been a noted target for researchers marrying cannabinoid science and dermatology. Studies reviewed by the authors found that anandamide, a prominent endocannabinoid, possesses antipruritic (anti-itch) properties. One study found that the application of palmitoylethanolamide (PEA), which activates anandamide, decreased itch by 86.4% in participating patients. A Matrix cream produced by Stiefel Laboratories, which contains PEA, has also been shown to reduce the skin redness, pruritus, thickening, and dryness associated with atopic dermatitis by 58.6%.
Another study found that the application of a cream containing lipids and endocannabinoids completely resolved itch in 38% of a sample of 21 patients, with a significant improvement in reported pruritus by the entire cohort. 81% of patients also experienced complete resolution of dry skin.
Psoriasis and Cannabinoids
Psoriasis is a common skin condition in which the skin’s renewal cycle is accelerated, leading to dry, flaky, and itchy skin. Some studies have found that cannabinoids may help to inhibit this process. Derakshan et al. suggest that “the interaction between the immune and nervous system in psoriasis occurs through a cholinergic anti-inflammatory pathway and the endocannabinoid system.”
Studies included in the review put forward a number of theories behind the potential of cannabinoids in the treatment of psoriasis. These include the theory that THC induced inhibition of keratinocyte proliferation is brought about through peroxisome proliferative-activated receptor gamma (PPARg). CB1 activation also leads to a down-regulation of keratins involved in hyperproliferation.
Acne & Seborrhoea and Cannabinoids
Acne is another common skin condition, which is caused by the blockage of hair follicles and sebaceous glands with associated inflammation. The cause of these blockages can be attributed to numerous factors, however the exact mechanisms are not fully understood. Cannabinoids may have a role in the treatment of acne. Inhibition of CB2 receptors in human sebocytes has been shown to help suppress lipid production, which may indicate that CB2 antagonists may play a role in reducing overexpression by sebaceous glands. A sample of 11 human patients trialed a 3% cannabis seed extract cream over a 12-week period. A significant reduction in sebum production and redness was recorded at the conclusion of the study.
Many of the studies assessed by the researchers for their review demonstrated the potential of cannabinoids and manipulation of the endocannabinoid system as treatment pathways for a number of skin conditions. However, the processes by which cannabinoids act are still not completely understood. The researchers conclude by addressing the need for further well-conducted, controlled trials in this area.
It is believed that patients are increasingly seeking to manage health conditions – including dermatological disorders – with the use of natural, cannabis-based treatments. In fact, a study assessing the attitudes of dermatologists to cannabinoids found that “86% believe cannabinoids have medical benefits beyond treating pain and nausea, 68% foresaw using cannabinoids in dermatology and 94% believed it is worthwhile to further research the role of cannabinoids in dermatology.”