PracticalDermatology

The Farm Bill of 2018 removed hemp from the list of controlled substances, paving the way for its cultivation on US soil to supply the burgeoning CBD (cannabidiol) market. While the hemp and marijuana plants are both considered Cannabis sativa L., the legislated difference centers on the concentration of the psychoactive compound Tetrahydrocannabinol or THC. Those plants with less than 0.3% THC concentration are hemp (which is used for CBD extraction), and those above this threshold, marijuana. Now legal in all 50 states (with a few caveats), CBD’s use as an ingredient in aesthetic and therapeutic skincare will likely only increase in popularity.

CBD’s Potential Skin Applications

Humans rely on the endocannabinoid system for regulatory purposes. Two primary receptors, CB1R and CB2R, are present in numerous tissues, including the epidermis. At a high level of differentiation, it is useful to think of CB1R localized primarily to the central nervous system, responsible for the psychoactive effects of THC. Peripheral tissue contains a higher concentration of CB2R, with cannabinol as the primary ligand, the binding of which results in anti-inflammatory and immunomodulatory effects.

Where does this leave CBD? While it does not bind to either receptor, CBD modulates these receptors via allosteric inhibition, thereby blunting the CNS effect of THC binding to CB1R, for example. Binding does occur between CBD and other receptors, including the recently-discovered GRP55, as well as PPAR and TRPV receptors. This may explain the cutaneous effects of CBD, including anti-inflammatory and antioxidant effects (via the NRF2 pathway), normalization of keratinocyte differentiation, and reduction of sebum production when production has been altered. By targeting the TRPV receptors, which are involved with intercellular keratinocyte communication, CBD may also reduce itch, which, along with the reduction of inflammation, gives hope for CBD’s use in inflammatory skin conditions such as eczema and psoriasis.

As an OTC skincare product ingredient meant for aesthetic use, CBD holds promise but has little supporting data. The antioxidant effect alone may improve fine lines and wrinkles, erythema, and prevent UV- and pollution-induced damage. Most data produced involves only in vitro experimentation, with the applicability to in vivo use yet to be elucidated.

Need for Caution

Beyond the lack of evidence, other reasons exist to engender concern about the use of CBD as a skincare ingredient. The 2018 Farm Bill tasked the FDA to regulate the sale of CBD products as part of the Federal Food, Drug and Cosmetic Act, but the agency has yet to publish regulatory guidelines. In addition, the concentration of CBD may be variable; in a 2017 study published in JAMA by Bonn-Miller et al, researchers tested 84 CBD-containing oils, tinctures, and vapes purchased online. Only 30.95 percent were labelled correctly with the actual CBD concentration; the CBD oils had the most number of correctly-labelled concentrations at 45 percent, meaning over half still had CBD concentrations either above or below the listed value.

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The popularity of CBD-containing topical products has exploded in recent years, fueled by the change in classification of the hemp plant by recent legislation. However, both the scientific and regulatory environments have yet to mature enough to allow for evidence-based uses or reliable formulations of this ingredient. Dermatologists should counsel their patients on this reality.

Drs. Farris and Lain are co-founders of the Science of Skincare Summit, to be held October 28-30 in Austin, TX. For information: scienceofskincaresummit.com

1. Martinelli G, Magnavacca A, Fumagalli M, et al. Cannabis sativa and Skin Health: Dissecting the Role of Phytocannabinoids. Planta Med. 2021 Apr 13.

2. Baswan SM, Klosner AE, Glynn K, et al. Therapeutic Potential of Cannabidiol (CBD) for Skin Health and Disorders. Clin Cosmet Investig Dermatol. 2020;13:927-942

3. Bonn-Miller MO, Loflin MJE, Thomas BF, et al. Labeling Accuracy of Cannabidiol Extracts Sold Online. JAMA. 2017;318(17):1708-1709.