Back in the day, before I could get access to fancy CBD balms or THC oils, I used to curl up in bed and wait for my weed guy to bring me strong chocolate edibles. They helped to relieve my cramps—not necessarily because of the pain-relieving properties of magnesium or caffeine, but because a high dose of edible bud was all that seemed to ease otherwise sharp, nagging pain that kept me bedridden.

At the time I didn’t much care about the explanation, but it turns out there’s a science as to why THC tampons and topical period products have been spreading across the medical marijuana market to much fanfare. Though research specifically on periods and cannabis is generally unavailable—the result of bias against studying both menstruation and marijuana—a 2000 study by Joy J. Mack discusses the benefits of using weed to alleviate muscle spasticity. Her focus is specifically on those with multiple sclerosis and spinal cord injuries, but similar muscle spasticity is a symptom present in many individuals dealing with menstruation.

The key, Mack’s research explains, is that

Spasms are thought to originate in areas of the brain that control movement, including several sites with abundant cannabinoid receptors.

Small doses of cannabis were shown to increase animation among rodents who were feeling pain (though larger doses seemed to give them couch-lock). In an experiment on a 30-year-old with MS, a simple 5 mg dose of THC steadied his handwriting significantly.

The research done on MS patients cannot, of course, entirely be mapped onto the experiences of menstrual cramping in women, certain non-binary people, and a number of transgender men. But other similarities exist between the two circumstances: both the MS patients and people in the throes of PMS and menstruation experience nausea and anxiety, two symptoms that have been proven fixable by THC and CBD respectively.

Inflammation is also a significant part of menstrual cramping, the reason why anti-inflammatory painkillers like ibuprofen can help, and it’s a symptom that CBD has been shown to relieve in arthritis patients. CBD passes into the bloodstream through the vaginal walls, eventually making its way past the blood-brain barrier and into brain receptors related to muscle relaxation. All of this makes the location of the suppository a prime spot for uterine pain relief.

And even without modern research on the explicit connection between marijuana and cramps, there are studies of the body’s endocannabinoid systems that support the hundreds of years of precedence for the use of marijuana-based pain relief.

Some cramp-relieving marijuana products make a point of taking into account that THC and CBD are both necessary to reduce symptoms. Foria Relief “tampons”—gooey, cocoa butter-based vaginal suppositories—include 10 mg of CBD along with THC.

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Plenty of people are singing the praises of the product: Whitney Bell wrote in KINDLAND that it “slowly creeps up on you” like an edible to the point that she was “almost numb down there.” Stefanie Jesney explained to Harper’s Bazaar that she felt that her “abdominal muscles released and a calm akin to a very restorative yoga class washed over [her] body [with] no psychoactive effects.” For Broadly writer Mish Barber Way, her cramps “totally disappeared […] within 20 minutes.”

But because everyone’s body is different other users, like me, didn’t feel the relief that they were looking for. Suzannah Weiss wrote for Glamour that she felt “relaxed and tired” and “clear-headed” but not “numb down there like she [had expected].” Personal experience has shown that this amount of CBD might not necessarily be enough to do the work of a couple of Advil or a stronger painkiller. But for people with minor amounts of cramping or who prefer to keep their health treatments holistic, these suppositories and similar products might be a game changer when it comes to the otherwise limited range of available options for period pain.