Hemp oil can be absorbed through the skin, but the extent of this absorption depends on the oil type and product formulation. It is important to distinguish between two products labeled “hemp oil.” Hemp Seed Oil, derived from the seeds of the Cannabis sativa plant, is rich in omega fatty acids but contains negligible amounts of cannabinoids like Cannabidiol (CBD). CBD-rich Hemp Extract, often called “CBD oil,” is extracted from the plant’s flowers, leaves, and stalks and is the source of the active compounds. The skin is primarily designed as a protective barrier, making the successful absorption of external molecules, including cannabinoids, a complex challenge.
The Skin’s Role as a Permeability Barrier
The skin’s primary function is to act as a defense against the external environment, preventing the entry of foreign substances and protecting against water loss. The outermost layer of the epidermis, the stratum corneum (SC), serves as the main obstacle to molecular absorption. This layer is described using a “bricks and mortar” model, where protein-rich cells (corneocytes) are held together by a lipid-rich matrix of ceramides, cholesterol, and fatty acids. This lipid-heavy structure makes the SC resistant to water-soluble substances. For a molecule to be absorbed, it must navigate this dense, lipophilic maze, which significantly limits the passage of most topical compounds.
Pathways for Molecular Penetration
Molecules attempting to cross the skin barrier must utilize specific routes to reach deeper layers. The two main pathways are the transcellular route (passing directly through the corneocytes) and the intercellular route (weaving through the lipid matrix between the cells). Cannabinoids like CBD are highly lipophilic (fat-soluble), which favors penetration of the lipid-rich stratum corneum. However, their relatively large molecular size presents a significant hurdle. Optimal skin penetration is achieved by molecules that are small, ideally under 500 Daltons, and possess the correct balance of lipid solubility. Since cannabinoids are typically larger than this ideal size, their bulk slows their passage considerably.
Localized vs. Systemic Effects
The destination of the absorbed compound determines if the application is topical or transdermal. Topical application is intended for localized relief, where active compounds penetrate the skin layers to interact with receptors in the epidermis and dermis but do not enter the bloodstream in significant amounts. This mechanism is sufficient for addressing localized issues such as muscle soreness, joint pain, or skin inflammation. Transdermal delivery, in contrast, aims for the compound to pass completely through the skin layers and enter the systemic circulation for a whole-body effect. Achieving systemic therapeutic concentrations of cannabinoids via standard topical creams is difficult because of the skin’s efficiency as a barrier.
Maximizing Absorption: Role of Formulations
Formulation science plays a role in enhancing the absorption of hemp oil’s active compounds. Manufacturers incorporate chemical penetration enhancers into topical products to temporarily disrupt the stratum corneum barrier. These enhancers, which can include alcohols, glycols, or natural terpenes, work by increasing the fluidity of the SC’s lipid matrix or creating aqueous channels. The choice of carrier oil also significantly impacts the diffusion rate and efficacy. Specialized delivery systems, such as microemulsions or nanoparticles, are being explored to encapsulate cannabinoids, allowing them to bypass the SC more effectively and maintain a sustained release profile.