Updated: May 25, 2020
While early research suggested cannabinoid receptors were only present in the brain and nerves, scientists later discovered they're present throughout the body, especially at high concentrations in the skin. Dr. Cheryl Bugailiskis, MD, a board-certified pediatrician recently interviewed by Bustle, explains:
"The skin is our largest organ and our body’s first line of defense against unwanted organisms. As such, this protective layer has the highest amount and concentration of cannabinoid receptors."
It turns out the “classic” CB1 and CB2 receptors of the endocannabinoid system are present in practically all cell types of the skin. Now, through experimental efforts over the last two decades, studies have confirmed that cannabinoid signaling is deeply involved in the maintenance of skin homeostasis, barrier formation and regeneration. These findings suggest the skin is a powerful conduit for CBD's therapeutic properties. As one scientific study put it, "The skin possesses a robust capacity to synthesize and respond to cannabinoids."
Furthermore, cannabinoids are lipophilic and love to hang out in fatty tissues. For instance, even if you don't apply cannabis topically and opt to smoke or ingest it, cannabinoids still get deposited into your fatty tissues. That's why THC is a notoriously difficult substance to eliminate from one's body. The prolonged retention of THC in fat in cannabis users is responsible for the prolonged detection of THC in urine tests. In essence, the skin seems to soak up cannabinoids like a sponge, no matter how they enter the body. This isn't a coincidence. Many argue the body is specifically designed to store CBD in fat cells and release cannabinoids gradually in order to treat chronic conditions.