Do ethnic skin differences affect how topical CBD products work on black skin?
1. The purpose of topical CBD products
In addition to products like oils and gummies, CBD can take the form of bath bombs, lotions, face masks, and lip balms, all of which are typically made for topical use. That means the topical CBD is applied to a local area like overlying a sore joint or muscle. That should be distinguished from transdermal CBD, which is designed to get to the dermis by way of a patch or salve.
- Cannabis company Joy Organics states, “Topical CBD cream provides targeted and localized support to muscle, joints and skin. It works to promote wellness through the ingredients in the topical formula.” Musculoskeletal injury, arthritis and back pain are some of the conditions for which topical CBD products are used.
- Reports find that topical CBD-enriched ointments/creams/lotions can help alleviate primary skin inflammatory conditions such as psoriasis, eczema, and acne
2. Structure of the skin
To understand how topical CBD products can help us, we need to first look at the basic structure of skin.
The skin is a multi-tasking organ, and the largest in the body by surface area. It protects us from invading microbes, toxins, and allergens; acts as a barrier to prevent water loss, and hence, dehydration; regulates temperature via the contraction and dilation of the blood vessels near the skin’s surface; manufactures melanin and Vitamin D.
The epidermis is the top of the three basic levels of the skin. It too, contains five sub-layers.
- The stratum corneum is the top layer of the skin made up of dead keratinocytes that renew every couple of weeks. It helps to retain skin moisture.
- Stratum lucidum is a transparent layer present only the palms and soles.
- Stratum granulosum is the keratinocyte layer. Keratinocytes produce keratin, a major component in hair, nails and skin.
- Stratum spinosum is made up of squamous cells that create the young keratinocytes that will migrate upward, and it also contains Langerhans cells, which helps to fight infection.
- Stratum basale (or basal level) consists of columnar cells, the older ones of which are pushed upward and transform to flatter cells. This level also has melanocytes, which make melanin pigment for protection against UV rays.
The dermis is the middle and thickest layer of the skin, containing connective tissue, capillaries, nerve endings and hair follicles. Dense collagen bundles give the skin its elasticity and suppleness. The dermis takes part in temperature regulation and supplies the epidermis with nutrients, and it does thin out with age.
The subcutaneous layer contains fat, connective tissues, larger blood vessels, and nerves. Most of the body’s fat is stored here as energy reserves, and it helps in regulation of temperature and serves as an attachment for muscles and bones.
3. How topical applications get into the skin
We know that certain medications like fentanyl, estradiol, testosterone, and nitroglycerine are effective for different medical conditions, so clearly they work. To do that, they must get past the stratum corneum and penetrate as far as the dermis, where the capillaries are. When the medication gets into the bloodstream, this is called absorption. How do these medications reach the dermis?
The molecules of the medications diffuse into the stratum corneum in a zigzag pattern in between the cells, which are arranged in a “brick-and-mortar” fashion. The corneum is resistant to both water-soluble and oil-soluble substances, and is the first formidable obstacle to penetration. If the stratum corneum is disrupted or partially removed, then penetration into the deeper epidermis is enhanced. This is shown clearly with fluorescent materials applied to experimental skin. A stained cross-section of the skin reveals that it gets to the dermis.
Turning now to how topical CBD products work, just as with the medications mentioned above, the epidermis, particularly the stratum corneum, is the major barrier to reaching the dermis. If the epidermis is removed by a burn to the skin, for example, molecules from certain medications like silvadene can theoretically be absorbed into the bloodstream.
Apart from the permeability of the stratum corneum, other factors affect how well the skin absorbs a substance.
- Particle size of the medication: Larger molecules won’t get very far into the skin, e.g. zinc oxide doesn’t penetrate well or at all. Olive oil and lanolin, on the other hand, penetration well.
- Stratum corneum hydration improves penetration and absorption. Ointments moisten the corneum layer and make the molecules pass through more easily. Application of hydrating lotions is best done after showering.
- Time of contact: the longer the substance is on the skin, the better.
- Skin temperature: the warmer the skin, the better the penetration and/or absorption.
4. Ethnic skin differences
To understand how topical CBD products work on black skin, we should consider how black skin differs from the skin of other groups.
- The increased melanin in black skin is photoprotective and renders black skin more resistant to aging. Therefore the onset of aging changes is earlier in white skin.
- One review article suggests that black skin is more resistant to allergens and irritants than white skin.
- Black skin has a more compact SC, i.e. although it isn’t thicker, there are more layers packed more tightly together.
- The barrier function of the SC in blacks appears to be stronger with more cell cohesion, although not all studies agree.
- Increased sebum (lipids) production and pore size is present in black skin.
- Desquamation of dead keratinocytes from the SC occurs more in black skin than in others, and the release and evaporation of water coming up from the dermis, which is called Trans-Epidermal Water Loss is also greater. This is probably why African Americans are always so conscious of the “ashy look” after showering, especially a hot shower.
Whether the superior barrier function of the stratum corneum in black skin has any significant effect on penetration and absorption of CBD topical products hasn’t been reliably studied. The density of the SC may be only one factor among many others affecting absorption, e.g. the lipid environment of the corneocytes. But if indeed absorption rates are impaired, it could prompt the development of more effective CBD carriers via transdermal patches for more efficient delivery of the CBD.