Skin cells have their own cannabinoid receptors, and many cannabis creams and balms are sold on that fact alone. This two-part article separates two things: what receptor research shows in the laboratory, and what trials have measured in people. Part 1 explains how the skin’s cannabinoid system works and why cannabinoids have trouble passing through skin. It then covers the trials in eczema, psoriasis and acne.
1. Why the Skin Became a Sales Target
Putting something on the skin feels safer than swallowing it. A swallowed dose goes through the liver first, and the liver breaks down part of it before it reaches the blood. This is called first-pass metabolism. A cream skips that step. It also keeps the dose in one area that you can see.
Researchers then found cannabinoid receptors on skin cells. Sellers soon used this finding to market cannabis skin products. The biology is interesting, but the evidence from patients is thin. This article keeps the two apart.
Nothing here is a recipe or a recommendation. Thailand’s controlled-herb rules, in force since 26 June 2025, restrict the sale of cannabis flower and ban advertising it. Skin products made with cannabis or hemp ingredients fall under separate Thai product rules. Do not assume a cream may be sold or advertised freely.
Translator’s note: In Thailand, cannabis flower (ช่อดอกกัญชา) is a controlled herb. This comes from the Notification of the Ministry of Public Health Re: Controlled Herbs (Cannabis), B.E. 2568, issued under the Thai Traditional Medicine Protection Act B.E. 2542, and in force since 26 June 2025. Flower may be sold only against a PT 33 (ภ.ท.33) prescription, for no more than 30 days of use. Advertising flower and selling it online are both prohibited.
Translator’s note: Extracts containing more than 0.2% THC may be licensed only to three kinds of holder. These are Thai juristic persons that are not “foreign” under the Foreign Business Act B.E. 2542, state agencies, and the Thai Red Cross Society. This comes from the Ministerial Regulation on Cannabis or Hemp Extracts B.E. 2569, in force since 26 April 2026. Processing or selling a controlled herb without a licence (Section 46) carries up to 1 year in prison, a fine of up to 20,000 baht, or both (Section 78). A grower who wants to make a balm from their own flower and sell it should first check which licence covers that activity.
What to do: Before you make, sell or recommend a cannabis skin product, check which licence covers that activity in the licensing topic. That tells you whether you need a licence before you start.
2. The Skin’s Own Cannabinoid System
Where the receptors are
The endocannabinoid system is the body’s own signalling network, and cannabis compounds act on it. It is found throughout the body, not only in the brain. The part in the skin is called the cutaneous endocannabinoid system (“cutaneous” means “of the skin”). It has three parts:
- receptors on the surface of cells;
- fat-based messenger molecules that the body makes to switch those receptors on, mainly anandamide and 2-arachidonoylglycerol;
- enzymes that make these messengers and then break them down.
A 2005 study of human skin tissue, published in the Journal of Dermatological Science, located the two main receptors. These are cannabinoid receptor type 1 and cannabinoid receptor type 2. The study found them on sensory nerve fibres. It also found them on hair follicles and sebaceous glands, which are the glands that make skin oil.
A 2023 review in the International Journal of Molecular Sciences adds two more cell types. One is the keratinocyte, the main cell of the skin’s outer layer. The other is the mast cell, an immune cell that releases itch and inflammation signals.
How well it is understood
Less well than product marketing suggests. A 2009 review in Trends in Pharmacological Sciences described this system as a therapeutic “opportunity”. In scientific writing, that word means the research was not finished yet.
Most later work did one of two things. It mapped where the receptors sit, or it tested compounds on cells in a dish. Little of it measured what happens in living people. A receptor below the skin surface matters only if the molecule actually reaches it.
What to do: If a product says it “works on the skin’s endocannabinoid system”, ask the seller for a study done in people, not in cells. A cell study gives a reason to run a trial. It does not show that the cream works.
3. Topical Versus Transdermal
Two different designs
| Feature | Topical | Transdermal |
|---|---|---|
| What it is designed to do | Act in or just under the treated skin | Pass through the skin into the bloodstream |
| Blood levels | Low or undetectable, on purpose | Meaningful, and intended |
| Usual form | Cream, balm, salve, lotion | Patch, or a gel that releases the drug at a controlled rate |
| Usual legal category | Often a cosmetic | Almost always a medicine |
Why most “transdermal” labels are wrong
An oily balm with cannabidiol (CBD) dissolved in it is a topical, whatever the label says. A real transdermal product is defined by two numbers. The first is how much drug it delivers per hour. The second is the blood level it produces. If a product gives neither number, the word “transdermal” has no data behind it.
A real transdermal product looks different. An open-label trial (one where participants know what they are using) was published in Scientific Reports in 2024. Fifteen people completed it. They applied a 4% cannabidiol transdermal gel, about 30 mg of cannabidiol a day. Cannabidiol and its breakdown products (metabolites) turned up in every urine sample.
Translator’s note: For a grower or buyer, there is nothing here to copy at home. Controlled-release patches and gels are made in pharmaceutical factories. The practical first step is to ask any seller who uses the word “transdermal” for the delivery rate per hour and the blood-level data.
What to do: If the seller cannot show those two numbers, treat the product as an ordinary topical. Do not pay a higher price for the word “transdermal”.
4. Why Cannabinoids Have Trouble Getting Through Skin
The stratum corneum is the skin’s outermost layer of dead cells. It is the main barrier. Molecules pass through it well when two conditions are met. First, they are small: under about 500 daltons, a unit of molecular weight. Second, they are balanced between oil and water.
Scientists measure that oil-versus-water balance as the partition coefficient, written logP. Molecules with a logP of about 1 to 3 cross the barrier best. Cannabinoids do not fit this range. A 2022 review in Pharmaceutics puts their logP at 6 to 7, which means they strongly prefer oil. They also dissolve very poorly in water.
As a result, cannabinoids enter the dead outer layer easily and then stay there. They build up in dead tissue instead of moving down to living cells. Their strong preference for oil is not an advantage for skin products. It is the main reason skin delivery is hard.
Researchers are testing ways to get past the barrier. Approaches under study include:
- chemical penetration enhancers, which loosen the barrier;
- nanocarriers such as liposomes, which are tiny fat bubbles that carry a drug;
- microneedles;
- prodrugs, which are modified molecules that the body converts back into the active drug.
A 2024 review in Cannabis and Cannabinoid Research notes that detailed clinical trials of cannabinoid skin delivery are still limited.
The gains measured so far are small. A 2023 study in Pharmaceutics put cannabidiol into organosilane particles (a silicon-based carrier). The researchers tested it on human skin that had been removed from the body (excised skin). The particles moved 0.41% of the applied dose into the lower epidermis and dermis, which are the living skin layers. Plain cannabidiol moved 0.27%. That is about 50% better, but still under 1% of the dose. The authors themselves stated that this stayed below therapeutic levels.
Translator’s note: Some products advertise “nano” or “liposome” cannabidiol. In the laboratory test above, the improved carrier still delivered less than 1% of the dose to the living skin layers. A label word does not tell you how much reaches the skin.
What to do: Before you pay more for “nano” or “liposome” claims, ask for skin-penetration data on that exact product. That shows whether the higher price buys anything measurable.
5. Eczema (Atopic Dermatitis)
Eczema, also called atopic dermatitis, is a long-term condition that causes dry, itchy and inflamed skin. Much of the eczema evidence credited to cannabis is not about plant cannabinoids at all. It is about palmitoylethanolamide, a fatty molecule that the body makes itself.
Palmitoylethanolamide is related to the cannabinoid system but works differently. It acts through receptors inside the cell nucleus. It also raises the general activity of the body’s own cannabinoid signalling. It does not switch on cannabinoid receptors directly.
The study cited most often is ATOPA, published in 2008 in the Journal of the European Academy of Dermatology and Venereology. It ran at several centres. It was observational and uncontrolled, which means there was no comparison group. The study included 2,456 patients aged 2 to 70. They used a barrier cream containing physiological lipids (fats similar to those in healthy skin) and palmitoylethanolamide.
ATOPA reported less redness (erythema), less itch (pruritus), less dryness and less use of steroid creams. The sample was large, but the design was weak, for two reasons. Moisturisers alone help eczema. Eczema also gets better and worse on its own. Without a comparison group, nobody can tell how much of the improvement came from the palmitoylethanolamide.
A stronger trial came in 2024. Rao, Moussa, Erickson and Briskey published it in Skin Pharmacology and Physiology. It was randomised and double-blind, so neither the patients nor the researchers knew who received which cream. It enrolled 72 adults, and 65 completed it. One group used a palmitoylethanolamide cream and the other used an ordinary moisturiser, for four weeks. The palmitoylethanolamide group improved more on two measures of eczema severity.
Evidence for cannabidiol itself is thinner. A 2019 study by Palmieri and colleagues gave a cannabidiol ointment to 20 patients with no comparison group. Only five of them had eczema; the others had psoriasis or scars.
Translator’s note: A palmitoylethanolamide cream contains no cannabis. A jar with a cannabis leaf on it may be relying on palmitoylethanolamide, not on cannabinoids. Read the ingredient list to see which one it actually contains.
What to do: If you or a family member has eczema, keep using the treatment a doctor prescribed. Show the doctor the ingredient list of any cream you want to add. Take a photo of the same skin area once a week for four weeks. This shows whether a change lasts longer than eczema’s normal ups and downs.
6. Psoriasis
Psoriasis causes thick, scaly patches (plaques) where skin cells multiply too fast. That makes the laboratory case easy to follow. In 2007, Wilkinson and Williamson reported results in the Journal of Dermatological Science. Four cannabinoids all slowed the growth of human keratinocytes grown in a dish. These were tetrahydrocannabinol (THC), cannabidiol, cannabinol and cannabigerol.
The effect grew stronger as the dose went up. Cannabinoid receptor types 1 and 2 could not explain most of the effect.
For about ten years afterwards, almost no human studies followed. The largest human study so far is Thai. Puaratanaarunkon, Sittisaksomjai and colleagues reported it in 2022. It was randomised, placebo-controlled and run at two centres. It included 51 patients with mild plaque psoriasis.
The study used a split-body design. Each patient put a 2.5% cannabidiol ointment on one area and a placebo on a comparable area. That way each person served as their own comparison. The trial lasted 12 weeks. Areas treated with cannabidiol scored better than placebo areas, and no side effects were reported. The authors called the result a favourable trend. They presented it as groundwork for future studies.
Translator’s note: This study is especially relevant to readers here because it was done in Thailand. It still tested one ointment, in mild psoriasis only, in 51 people. It does not show that balms sold in shops work.
What to do: If you have psoriasis, take the study reference to a dermatologist. Ask whether it applies to your case. Do not stop prescribed treatment while you wait for an answer.
7. Acne and the Sebaceous Gland Study
What the laboratory work showed
The study cited most often is by Oláh and colleagues, published in the Journal of Clinical Investigation in 2014. They applied cannabidiol to human sebaceous gland cells from a line called SZ95. These cells are “immortalised”, which means they keep dividing in the laboratory indefinitely. The researchers also used human skin kept alive in a dish (organ culture).
Cannabidiol had three effects:
- it reduced the oil production triggered by acne-promoting substances;
- it slowed cell multiplication without killing the cells;
- it reduced inflammatory signals called cytokines.
It acted through two routes. One is TRPV4, an ion channel (a gate in the cell membrane that lets charged particles through). The other is the adenosine A2a pathway, a receptor system for the signalling molecule adenosine.
This was not a study in people. Cells and skin in a dish have no barrier to cross, no blood supply, no immune system and no acne bacteria in the hair follicles. The result gives a reason to run a trial in people, and nothing more.
What happened in people
Botanix Pharmaceuticals then ran a Phase 2 trial of BTX 1503, a synthetic cannabidiol solution. Phase 2 is a mid-stage trial that tests whether a drug works and which dose to use. The trial lasted 12 weeks and was randomised and double-blind. It was vehicle-controlled, meaning the comparison group used the same solution without cannabidiol. It enrolled 368 patients with moderate-to-severe acne, and the results came out in October 2019.
The trial’s main efficacy measure was the change in the number of inflamed spots (lesions) after 12 weeks. In the results posted on ClinicalTrials.gov, inflamed lesions fell by 12 at the best dose (5% once a day), compared with 11.3 in the vehicle group. That is almost no difference.
What to do: When an acne claim rests on a laboratory study, look for the human trial that came after it. For cannabidiol, the largest such trial missed its main target. Keep your standard acne treatment.
Part 2 covers localised pain, itch, intoxication and drug tests, label accuracy, allergy risk, and a summary table of all the evidence. Questions about this part are welcome in the thread below. Post the ingredient list of any product you ask about.
References
- Study mapping cannabinoid receptor types 1 and 2 in human skin tissue. Journal of Dermatological Science, 2005.
- Review of the cutaneous endocannabinoid system. International Journal of Molecular Sciences, 2023.
- Review of the skin’s endocannabinoid system as a therapeutic opportunity. Trends in Pharmacological Sciences, 2009.
- Open-label trial of a 4% transdermal cannabidiol gel (15 completers). Scientific Reports, 2024.
- Review of cannabinoid properties for skin delivery. Pharmaceutics, 2022.
- Review of enhancers, nanocarriers, microneedles and prodrugs for cannabinoid skin delivery. Cannabis and Cannabinoid Research, 2024.
- Cannabidiol in organosilane particles on excised human skin. Pharmaceutics, 2023.
- ATOPA study. Journal of the European Academy of Dermatology and Venereology, 2008.
- Rao, Moussa, Erickson, Briskey. Randomised trial of palmitoylethanolamide cream in eczema. Skin Pharmacology and Physiology, 2024.
- Palmieri and colleagues. Uncontrolled study of a cannabidiol ointment in 20 patients with psoriasis, eczema or scars, 2019.
- Wilkinson, Williamson. Cannabinoids and keratinocyte proliferation. Journal of Dermatological Science, 2007.
- Puaratanaarunkon, Sittisaksomjai and colleagues. Randomised split-body trial of 2.5% cannabidiol ointment in mild plaque psoriasis. Journal of the European Academy of Dermatology and Venereology, 2022.
- Oláh and colleagues. Cannabidiol and human sebocytes. Journal of Clinical Investigation, 2014.
- Botanix Pharmaceuticals. Phase 2 results of BTX 1503 in moderate-to-severe acne, October 2019.
This article is part of the Asiannabis Community educational series on medical cannabis. It is general information, not medical advice. Treatment decisions belong with a licensed practitioner. Content is for educational purposes within jurisdictions where medical cannabis is legally permitted.
Continued in Part 2: Cannabis on the Skin: Pain, Itch, Drug Tests, Label Accuracy and Allergy Risk (Part 2 of 2)