If you’ve found relief from hot showers during CHS episodes, you’ve probably wondered: why does this actually work? A recent comprehensive review of the scientific literature looked at this exact question, and the answer is more complicated—and less certain—than you might expect.

The TRPV1 Theory: Plausible But Unproven

The most common explanation you’ll hear is that hot showers work by activating something called TRPV1 receptors. These are sensors in your body that respond to heat and certain chemicals (like capsaicin, the stuff that makes peppers hot). The theory goes that chronic cannabis use messes with these receptors, and hot water or capsaicin cream reactivates them, which somehow shuts down the nausea signals.

Here’s the problem: While this theory makes sense, there’s actually very little direct evidence to prove it.

A systematic review that analyzed over 183 research articles and 211 CHS patients found that only 3 out of 10 studies even discussed TRPV1 mechanisms in detail. And even those studies relied mostly on theoretical explanations and lab experiments, not actual measurements of what’s happening in people with CHS.

The review concluded that CHS pathophysiology remains unclear, with limited evidence supporting any single explanation—including TRPV1.

What We Know For Sure: Hot Water Works

Despite the uncertainty about why it works, the evidence that hot water does work is pretty clear. Studies show that 91-92.3% of CHS patients report relief from hot water bathing. That’s a remarkably consistent finding across multiple studies.

The relief is often immediate and dramatic, though temporary. People describe needing the water to be very hot—sometimes almost scalding—to get relief, and symptoms typically return once the body cools down.

Capsaicin Cream: Mixed Results

Capsaicin cream (applied to the abdomen) is supposed to work through the same TRPV1 mechanism as hot water. But the evidence here is more mixed:

• Small case studies report 100% success rates
• Larger, more rigorous studies show more modest effects or no significant benefit
• Some studies found pain reduction (from 8 to 5.5 on a pain scale), but this could also be due to natural symptom cycling or other treatments given at the same time

This pattern—where smaller studies show dramatic results but larger studies are more cautious—suggests we need better research to really understand capsaicin’s effectiveness.

Alternative Explanations

The research review found several other possible explanations for why hot showers help:

1. CB1 receptor effects: Some researchers propose that hot water helps restore normal body temperature regulation that’s been disrupted by chronic cannabis use through CB1 receptors (the main receptors that THC binds to). This theory doesn’t involve TRPV1 at all.
2. Natural symptom cycling: CHS symptoms often come in cycles. It’s possible that some of the relief people experience is just the natural ebb and flow of symptoms, not necessarily the hot water itself.
3. “Cutaneous steal” syndrome: This theory suggests that hot water redirects blood flow to the skin and away from the gut, which might reduce nausea and vomiting.
4. Multiple mechanisms: It’s also possible that several of these mechanisms work together, rather than one single explanation.

What’s Missing: The Research Gaps

The review identified several critical gaps in our understanding:

1. No direct measurements: No studies have actually measured TRPV1 receptor activity in CHS patients before and after hot water or capsaicin treatment
2. No comparison studies: We don’t have studies comparing TRPV1-activating treatments with similar heat/irritant sensations that don’t activate TRPV1
3. No biochemical data: There’s no data on substance P levels, TRPV1 receptor density, or downstream signaling in CHS patients
4. Inconsistent effectiveness: If hot water and capsaicin work through the same TRPV1 mechanism, why is hot water almost universally effective while capsaicin shows mixed results?

What This Means For You

If you’re using hot showers to manage CHS symptoms, here’s what matters:

The good news: The evidence is clear that hot water helps most people with CHS. The fact that we don’t fully understand why doesn’t change the fact that it works for you.

The reality check: Hot showers are a symptom management tool, not a cure. The underlying problem—whatever it is—is still there when you step out of the shower.

The bottom line: Scientists are still figuring out the exact mechanism. TRPV1 receptors might be involved, or it might be something else entirely. What we know for sure is that hot water provides relief for the vast majority of people with CHS, and that’s what matters most when you’re in the middle of an episode.

The Need For Better Research

The review authors called for:

• Prospective studies that directly measure what’s happening in the body
• Randomized controlled trials to properly test treatments
• Basic science research to understand the underlying pathophysiology
• Large-scale studies to get more reliable answers

Until we have that research, TRPV1 activation remains a plausible but unproven hypothesis—one possible explanation among several, but not a confirmed fact.

References

This article is based on a systematic review that analyzed research from multiple sources, including:

• Moon et al. (2017) – Case report on capsaicin treatment
• Pourmand et al. (2021) – Systematic review and meta-analysis of capsaicin
• Sorensen et al. (2016) – Large systematic review of CHS pathophysiology
• Simonetto et al. (2011) – Case series of 98 CHS patients
• Richards et al. (2017) – Pharmacologic treatment review
• Dezieck et al. (2017) – Case series on capsaicin in emergency departments

For the full analysis see below:

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Remember: While understanding the science is interesting, what matters most is finding relief and getting proper medical care. If you’re experiencing CHS symptoms, talk to a healthcare provider about your options, including the only proven long-term solution: stopping cannabis use.