Why does weed makes my mouth feel so dry?

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I enjoy partaking in the herb every now and then, especially now, savoring the high it brings as a brief reprieve from the coinciding stressors of a pandemic and worldwide racial reckoning. But cannabis, like any substance, can have side effects. One of my least favorite: It leaves the inside of my mouth parched AF, an annoying phenomenon commonly referred to as "cotton mouth." As a health reporter who also loves her edibles, I’m curious as to why weed makes my mouth feel dry, and what, if anything, I can do about it. I reached out to scientists to investigate.

At first, people simply blamed it on the particulates in the smoke formed when you light up, since cigarette smoking can dry out your mouth, too, says Lewis Nelson, professor and chair of the department of emergency medicine and chief of the division of medical toxicology at Rutgers New Jersey Medical School. But, “it’s also become pretty clear over the years that you can get dry mouth from pot brownies and gummy bears,” he tells me. (The last time I experienced it, I was sipping on cannabis-infused seltzer water.) “It’s a direct effect of THC,” short for tetrahydrocannabinol, the compound in cannabis that makes you feel high.

First, let’s back up, and walk through what THC actually does in your body: A cell signaling system, known as the endocannabinoid system, regulates sleep, appetite, and a bunch of other biological functions, Healthline explains. It consists of molecules your body makes on its own, known as endocannabinoids, which, in turn, bind to endocannabinoid receptors, located in numerous regions of your body. As it turns out, THC mimics the activity of endocannabinoids, binding to the same receptors as they do.

When THC binds to the endocannabinoid receptors on your salivary glands, it “reduces the amount and increases the viscosity” of the saliva they secrete — hence the dry, sticky feeling inside your mouth.

Among these receptors are those found on your salivary glands, including the major glands nestled around the back of your lower jaw. The binding of THC to these receptors inhibits the parasympathetic nervous system (PNS), responsible for “rest and digest” functions, such as slowing your heart rate, moving food through your digestive tract — and, increasing your saliva production.

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Indeed, “things that block the PNS cause you to have a dry mouth,” Nelson says. When THC binds to the endocannabinoid receptors on your salivary glands, it “reduces the amount and increases the viscosity” of the saliva they secrete — hence the dry, sticky feeling inside your mouth. You might’ve noticed that your mouth also feels dry when you take Benadryl and other antihistamines; that’s because they, too, block the PNS, but by binding to different receptors.

How you imbibe doesn’t really matter, Nelson explains. In other words, taking an edible won’t make you more likely to experience a dry mouth than smoking a joint, since the THC in your weed doesn’t bind to the endocannabinoid receptors on your salivary glands right away—instead, it circulates through your bloodstream to reach those glands.

While it might be tempting when the inside of your mouth feels like sandpaper, Nelson cautions against gulping down massive amounts of water. Although not producing enough saliva is a symptom of dehydration, your body isn’t actually dehydrated, “it’s just that the glands are shut down.” He notes that some people suck on candy to keep their saliva flowing. Also, try to lower your intake of alcohol, which can also reduce saliva secretion, suggests Yu-Fung Lin, an associate professor of physiology and membrane biology at UC Davis.

While you can minimize mouth dryness to some extent, you might also just need to accept it as a trade-off to getting high, Nelson says. But for the moment of chill cannabis offers when I do occasionally use it, it’s a trade-off I’m willing to make — I’ll just suck on some Smarties while I’m at it.