Is There THC In Sweat?


Forensic Science International looked into the phenomenon of ‘sweat testing’ and their findings were published by the National Institute of Health.

Tiffany King
Aug 19, 2017

We’ve heard lots about sweating out THC via workouts or the sauna to eliminate it from the body. Since delta-9Tetrahydrocannabinol (THC) binds to the body’s fat cells, it makes total sense why most people recommend sweating it out before drug tests or for general detoxification purposes. But can THC really be found in our sweat, or is this just an assumption? Forensic Science International looked into the phenomenon of ‘sweat testing’ and their findings were published by the National Institute of Health.

THC is definitely present in sweat

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According to the study’s abstract, “Sweat testing is a noninvasive technique for monitoring drug exposure over a 7-day period in treatment, criminal justice, and employment settings.” To determine whether detectable THC would be present in sweat, researchers evaluated THC excretion in 11 daily cannabis users after they’d recently quit smoking pot.

The patches were worn for 7 days during each subject’s period of monitored abstinence and were found to have THC levels “above the United States Substance Abuse Mental Health Services Administration’s proposed cutoff concentration for federal workplace testing of 1 ng THC/patch.”

After two weeks, eight out of 11 subjects’ patches tested negative for THC and one subject had positive THC patches after four weeks of abstinence.

So yes, THC is most definitely present in sweat and actually has a similar elimination period as that of urine, given that it can take a week or more to clear on a sweat test.

This explains why many people attempting to flush out THC report that their sweat smells like weed. The terpenes and other compounds present in cannabis can definitely impact the smell of these excretions.

Does the ingestion method make a difference?

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Also tested were seven separate subjects who were given oral THC of up to 14.8 mg daily for five consecutive days. Interestingly, the oral THC users registered below the cutoff for workplace testing during all phases of the study, which led researchers to conclude that though most daily cannabis users will have sweat that tests positive within the first week of cessation, “oral ingestion of up to 14.8 mg THC daily does not produce a THC positive sweat patch test.”

The above-referenced study seems to have concluded that smoked THC more readily shows up in our sweat than ingested THC. “This controlled administration study demonstrated that THC does not readily enter sweat following oral ingestion.”

The theory is that less THC hits the bloodstream when ingested due to its absorption in the stomach and the metabolic process. Whereas smoking immediately hits the bloodstream and becomes concentrated within the blood plasma. Of course, ingesting edibles in higher doses than 14.8 mg may lead to the increased presence of THC in sweat.

What about CBD?

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A subsequent study found that blood plasma concentrations of THC appeared to be higher when CBD was taken simultaneously, however, CBD itself does not “appear to enter sweat in amounts that are detectable with current techniques.”

Tiffany King
Aug 19, 2017