A laboratory study in mice reports that activating cannabinoid type 1 (CB1) receptors reduced sweating. Researchers suggest the endocannabinoid system may help regulate sweat glands, much as it appears to regulate tear and saliva production. This is early, preclinical research in animals. It does not show a benefit in people, and it is not evidence that any cannabis-based product treats a sweating disorder.
Key Findings:
- The endocannabinoid system helps regulate many body processes, including mood, body temperature and the activity of exocrine glands such as the tear and salivary glands.
- In this mouse model, activating cannabinoid receptor type 1 (CB1) reduced the galvanic skin response and basal sweating measured in the animals’ hind paws.
- Of the two main plant cannabinoids tested, tetrahydrocannabinol (THC) reduced sweating in mice; cannabidiol (CBD) did not.
- The researchers propose that CB1 receptors on the nerves supplying sweat glands dampen sweating, mirroring what has been reported for tearing and salivation.
- The authors say the findings may support further laboratory and, eventually, clinical investigation. They are not evidence of benefit in humans.
Why researchers are interested in cannabinoids and sweat glands
Cannabis use has long been associated with dry eyes and dry mouth. That observation led scientists to ask whether the endocannabinoid system turns down the activity of glands that produce tears and saliva.
A recent mouse model of hyperhidrosis employed a galvanic skin response-based assay to investigate cannabinoid regulation of sweating in awake, unanaesthetised mice. Earlier work by the same group reported that CB1 receptors influence the lacrimal (tear), submandibular and parotid (salivary) glands.
Tear and salivary glands belong to a wider family of exocrine glands, which release fluids through ducts. Sweat glands are part of the same family. That raised an intriguing question: if the endocannabinoid system helps regulate tearing and salivation, might it also help regulate sweating? Alongside anecdotal reports of reduced sweating in some cannabis users, a single published case report has described reduced sweating in one person with hyperhidrosis. The researchers set out to test the idea systematically in an animal model.
Understanding how the body regulates sweating
In humans, sweating is essential for controlling body temperature. People have several types of sweat gland (eccrine, apocrine and apoeccrine), but it is the eccrine glands that do most of the work of cooling the body. When these glands malfunction, the consequences can be serious. Excessive sweating is known as hyperhidrosis; a near-absence of sweating is known as anhidrosis, which can be dangerous because the body cannot cool itself.
Sweating-related disorders are common, thought to affect tens of millions of people in industrialised countries, and they become more frequent with age. Current options are limited. Treatments such as botulinum toxin injections exist but are not suitable or effective for everyone. Understanding the biology of sweat regulation in more detail is a reasonable scientific goal, because a better understanding could, in the long term, help researchers identify new targets to study.
How did the study assess sweating in mice?
Mice cool themselves in several ways, but they do have eccrine sweat glands in their paws. The researchers adapted a galvanic skin response (GSR) sensor — the same basic technology used in human skin-conductance measurements — for use on the hind paws of awake, unanaesthetised mice. Pressing a sensor to each paw produced a conductance reading in microsiemens (µS); more sweat means higher conductance.
The team first checked that the method actually measured sweating. Pilocarpine, a drug that stimulates sweat glands, increased conductance as expected. Glycopyrronium (glycopyrrolate), a drug that reduces sweating and is used topically in people, lowered conductance. The assay also detected the natural decline in sweating that occurs with age. The researchers also measured body temperature before and after some treatments, and used immunohistochemistry to look for CB1 receptors in the paw tissue.
What were the findings of the study?
Cannabinoid receptor activation reduced sweating
The researchers tested several compounds that act on the endocannabinoid system:
- CP55940 — a non-selective cannabinoid receptor agonist that mimics some effects of tetrahydrocannabinol (THC)
- SR141716 (rimonabant) — a CB1 receptor blocker
- URB597 — a fatty acid amide hydrolase (FAAH) enzyme blocker (FAAH breaks down the body’s own cannabinoid, anandamide)
- JWH133 — a cannabinoid type 2 (CB2) receptor agonist
CP55940 substantially reduced the galvanic skin response in both male and female mice an hour after treatment.
To work out which receptor was responsible, the experiment was repeated in genetically modified mice. In CB2 “knockout” mice (which lack CB2 receptors), the effect remained; in CB1 knockout mice, it disappeared.
This points to the CB1 receptor as the route through which the effect occurs. The CB1 blocker SR141716 and the FAAH blocker URB597 did not change conductance. The CB2 agonist JWH133 modestly reduced conductance, but the same effect appeared in CB2 knockout mice, so it was not driven by CB2 activation.
Phytocannabinoid Effects on Galvanic Skin Responses
Next, two major cannabinoids, THC and cannabidiol (CBD), were tested for their effects.
THC (10 mg/kg) reduced the galvanic skin response in mice, while CBD (20 mg/kg) had no effect. The authors note that the null result for CBD is consistent with the only related human study to date. This was a trial of CBD and exercise that reported no effect on sweating.
Cannabinoids and Changes in Body Temperature
Cannabinoids can lower body temperature slightly, which could, in principle, reduce sweating on its own. To test this, the researchers used JWH018, a synthetic cannabinoid that produces a stronger drop in temperature than THC. JWH018 lowered body temperature by about 1.5°C but produced only a small reduction in baseline sweating — a 14% fall, compared with the 36% fall seen with THC. The authors conclude that lower body temperature is unlikely to be the main explanation for the reduced sweating.
CB1 Receptor Expression in Mice’s Walking Pads
Using immunohistochemistry, the researchers found CB1 receptors on nerve-like fibres surrounding the sweat glands; this staining was absent in CB1 knockout mice. They also detected the enzymes that make and break down anandamide (one of the body’s own cannabinoids) within the gland tissue. Together, this suggests a local CB1/anandamide circuit in the mouse paw. This is the same pattern the group has reported in the tear and salivary glands.
What do these findings tell us?
The most reasonable interpretation is that, in mice, activating CB1 receptors reduces sweating, probably by dampening the release of the nerve signal (acetylcholine) that tells eccrine glands to produce sweat. This adds to a broader picture in which the endocannabinoid system appears to turn down the activity of several exocrine glands.
Several important limits apply. This is an animal study, and mice do not rely on sweating for temperature control in the way humans do. The findings have not been confirmed in people. The supporting human evidence is limited to anecdotal reports and a single case report, and the one human trial of CBD found no effect. Whether these results translate to humans is unknown and would require well-designed clinical research to establish.
The authors describe their work as identifying a possible biological target worth investigating further. It is hypothesis-generating laboratory science, not a demonstration that cannabis, THC, or any cannabis-based product reduces sweating or treats a sweating disorder in people.
