Does a topical cannabinoid product enter the bloodstream?

It depends on the formulation. Most commercial balms and oils are not designed for transdermal delivery and produce minimal plasma cannabinoid levels — the molecule tends to stay in the upper skin layers. Patches and gel formulations with penetration enhancers can be engineered to achieve systemic absorption, which is a different pharmacokinetic goal entirely. Published permeation studies reflect whichever model was used, so it's worth checking the formulation type before interpreting the data.

Are topical cannabinoid products legal in Australia without a prescription?

It depends on the cannabinoid, its concentration, and whether the product makes any therapeutic claim. Hemp-derived products containing only trace cannabinoids and sold as cosmetics (without therapeutic claims) may sit outside TGA scheduling. Products that make a therapeutic claim, or that contain CBD above certain concentration thresholds, or any THC, are captured by the Poisons Standard and generally require prescription. If in doubt, the TGA's published guidance on cannabinoid scheduling is the authoritative reference.

What role do terpenes play in a topical cannabinoid formulation?

Several terpenes found in cannabis — including beta-caryophyllene and eucalyptol — are also recognised pharmaceutical penetration enhancers. In a full-spectrum topical formulation, their presence may influence how readily cannabinoids permeate the stratum corneum, independent of any receptor-level activity. This is an active area of formulation research, but controlled comparative data between full-spectrum and isolate topicals in human skin models is still limited.

Why is the log P value of CBD relevant to topical formulations?

Log P is a measure of lipophilicity — how strongly a molecule prefers an oily phase over a water phase. CBD's high log P (around 6) means it partitions readily into lipid-rich environments like the stratum corneum, but struggles to move through the aqueous layers of deeper skin. Formulators work around this by using emulsification systems, penetration enhancers, or nanocarriers to improve distribution across the skin's layered structure.

Topical Cannabinoid Formulations

By Tom Whitfield · 3 June 2026 · 7 min read

What the skin actually does to a cannabinoid

About three years ago I was cataloguing a batch of new journal acquisitions , one of those quiet Friday afternoons where the photocopier is mercifully silent , and I came across a 2019 review in the European Journal of Pharmaceutics and Biopharmaceutics that stopped me mid-page. The authors had modelled cannabidiol permeation across human skin and found that the lipophilicity that makes cannabinoids so chemically interesting is precisely what makes topical delivery complicated. Too oily for the aqueous layers, not quite right for the lipid bilayers. That tension sits at the heart of everything in topical cannabinoid formulation.

Skin is, by design, a barrier. The stratum corneum , the outermost layer; is a tightly packed arrangement of dead keratinocytes embedded in a lipid matrix. Molecules that want to cross it need to thread a narrow physicochemical needle: not too hydrophilic, not too lipophilic. Cannabidiol (CBD) has a log P (octanol-water partition coefficient) of around 6, which puts it firmly in the lipophilic camp. That means it tends to accumulate in the stratum corneum rather than pass through it readily. Whether a given formulation achieves local tissue deposition or systemic absorption depends enormously on how that lipophilicity is managed by the formulator.

Local versus transdermal: two genuinely different goals

This distinction is often glossed over, which I find a bit frustrating. A topical cannabinoid formulation can aim for one of two pharmacokinetic outcomes. The first is local deposition, cannabinoid molecules reaching the dermis and underlying tissue without meaningfully entering circulation. The second is transdermal delivery, where the formulation is engineered to push cannabinoids past the dermis and into the bloodstream, sidestepping first-pass metabolism in the liver. These are not the same thing, and they require quite different formulation strategies.

For local deposition, emulsions, balms and ointments with high lipid content can hold a cannabinoid in the upper skin layers. For transdermal delivery, formulators typically use penetration enhancers, compounds like ethanol, propylene glycol, or specific fatty acids; that transiently disrupt the stratum corneum's lipid organisation, creating a window for permeation. Patches designed for transdermal use sit at the more technically demanding end of this work. The bioavailability figures between these two approaches differ substantially, which is why published permeation studies can look contradictory if you don't check which model they used.

The receptor landscape under the skin

Why would a cannabinoid in the skin do anything at all? The answer lies in the endocannabinoid system, which is expressed in human skin to a degree that still surprises people when they first encounter the literature. Keratinocytes, sebocytes, hair follicle cells, mast cells, and sensory nerve fibres in the dermis all express cannabinoid receptors. CB1 receptors are found on cutaneous sensory nerve terminals. CB2 receptors appear on immune-active cells within the dermis. Endogenous ligands including anandamide are synthesised and degraded locally in skin tissue.

This means a cannabinoid molecule that reaches the dermis has a plausible molecular target, not just a vague surface interaction. The pharmacology here is genuinely interesting from a basic science standpoint. Whether that receptor activity translates into any particular outcome for a user is a separate question, and one where the current clinical evidence is, honestly, thinner than the preclinical literature implies it should be.

Formulation types and what separates them

The carrier matters as much as the cannabinoid. Here's how the main formulation classes differ in their delivery characteristics:

Oils and serums: High lipid content, limited penetration enhancement. Cannabinoids tend to stay in the upper stratum corneum. Simple to formulate; shelf stability is manageable with antioxidants.
Emulsions (creams, lotions): Oil-in-water or water-in-oil systems. The aqueous phase can carry water-soluble penetration enhancers. More complex to stabilise; emulsifier choice affects how the cannabinoid partitions at the skin surface.
Gels: Typically hydroalcoholic. Ethanol acts as both solvent and penetration enhancer. Faster evaporation from the skin surface can drive deeper permeation.
Patches: Matrix or reservoir designs. Provide controlled, sustained release and are the formulation class most associated with true transdermal delivery. Require the most rigorous permeation testing.
Nanoparticle systems (liposomes, niosomes, solid lipid nanoparticles): An active research area. Encapsulating a cannabinoid in a nanocarrier can improve stratum corneum penetration and protect the molecule from oxidative degradation. Most of this work is still preclinical.

THC and CBD are the most studied cannabinoids in topical models, but there is emerging preclinical interest in cannabigerol (CBG) for its interaction with skin receptor subtypes. Terpenes in full-spectrum preparations add another variable: several common cannabis terpenes, including beta-caryophyllene and eucalyptol, are themselves established penetration enhancers in pharmaceutical science, independent of any cannabinoid receptor activity. Whether that meaningfully alters the delivery profile of a full-spectrum topical compared with an isolate-based one is not yet settled.

The regulatory picture in Australia

Topical cannabinoid products occupy an interesting, and sometimes confusing; space under Australian law. The TGA's scheduling decisions under the Poisons Standard apply regardless of the route of administration. CBD in a topical formulation is still CBD under schedule classification; it does not become unscheduled simply because it is not ingested. Products containing CBD above the 150 mg/day threshold for the Schedule 3 low-dose oral carve-out, or formulations containing any THC, require prescription under Schedule 4 or Schedule 8 depending on their cannabinoid profile and concentration.

Practically, this means that most topical cannabinoid products available in Australia without a prescription either contain hemp-derived phytocannabinoids at concentrations below the relevant thresholds, or they are regulated as cosmetics under the Industrial Chemicals Act 2019 with no therapeutic claims permitted. Any product making a therapeutic claim needs to be listed or registered on the Australian Register of Therapeutic Goods (ARTG). The Special Access Scheme and Authorised Prescriber pathways exist for unapproved cannabinoid medicines, including topicals, where a prescribing clinician has determined their use is appropriate for a specific patient.

Good manufacturing practice matters here too. A topical formulation produced under GMP conditions is a fundamentally different product from one made outside that framework, not just in regulatory status but in demonstrated batch consistency and contaminant testing. I'd argue the market has been slow to communicate this distinction clearly to consumers, the labelling on many products tells you very little about how or where they were made.

What the clinical evidence actually looks like

I want to be straightforward here: the clinical trial base for topical cannabinoids is small. There are a reasonable number of in vitro permeation studies using synthetic skin models and ex vivo human skin, and a growing body of rodent data. Controlled human trials with topical formulations specifically (as opposed to oral or inhaled cannabinoids) are fewer than the volume of consumer interest would suggest they should be. Several trials have been conducted in specific dermatological contexts, but sample sizes are generally modest and methodological heterogeneity makes cross-study comparison difficult.

The pharmacokinetics work, measuring what actually reaches systemic circulation after topical application; is more consistent. Studies have generally confirmed that well-formulated emollient bases without penetration enhancers produce minimal plasma cannabinoid levels, supporting the idea that local tissue deposition rather than systemic absorption is the dominant outcome for most commercial topicals. That is a mechanistic finding, not a claim about efficacy.

The honest summary is: the basic science of how cannabinoids interact with skin and its receptor populations is genuinely interesting and reasonably well characterised. The clinical translation of that basic science into demonstrated outcomes for humans remains, at this point, an open research question.

Sources

, Tom Whitfield, Health librarian, references & fact-checking

Common questions

Does a topical cannabinoid product enter the bloodstream?: It depends on the formulation. Most commercial balms and oils are not designed for transdermal delivery and produce minimal plasma cannabinoid levels — the molecule tends to stay in the upper skin layers. Patches and gel formulations with penetration enhancers can be engineered to achieve systemic absorption, which is a different pharmacokinetic goal entirely. Published permeation studies reflect whichever model was used, so it's worth checking the formulation type before interpreting the data.
Are topical cannabinoid products legal in Australia without a prescription?: It depends on the cannabinoid, its concentration, and whether the product makes any therapeutic claim. Hemp-derived products containing only trace cannabinoids and sold as cosmetics (without therapeutic claims) may sit outside TGA scheduling. Products that make a therapeutic claim, or that contain CBD above certain concentration thresholds, or any THC, are captured by the Poisons Standard and generally require prescription. If in doubt, the TGA's published guidance on cannabinoid scheduling is the authoritative reference.
What role do terpenes play in a topical cannabinoid formulation?: Several terpenes found in cannabis — including beta-caryophyllene and eucalyptol — are also recognised pharmaceutical penetration enhancers. In a full-spectrum topical formulation, their presence may influence how readily cannabinoids permeate the stratum corneum, independent of any receptor-level activity. This is an active area of formulation research, but controlled comparative data between full-spectrum and isolate topicals in human skin models is still limited.
Why is the log P value of CBD relevant to topical formulations?: Log P is a measure of lipophilicity — how strongly a molecule prefers an oily phase over a water phase. CBD's high log P (around 6) means it partitions readily into lipid-rich environments like the stratum corneum, but struggles to move through the aqueous layers of deeper skin. Formulators work around this by using emulsification systems, penetration enhancers, or nanocarriers to improve distribution across the skin's layered structure.
What is the difference between a topical and a transdermal cannabinoid product?: Topical products are generally intended to deliver cannabinoids to the local tissue — skin layers and structures beneath — without significant entry into systemic circulation. Transdermal products are specifically engineered to push cannabinoids past the dermis and into the bloodstream, effectively using the skin as a drug delivery route. Patches are the most common transdermal format. The two approaches have different bioavailability profiles and different regulatory considerations under Australian law.