“Cold plunging keeps me from getting sick” is one of the most repeated claims in the hobby. It is also one of the hardest to test, because colds come and go on their own.
This article covers the studies behind the claim. It sits under our overview of cold plunge benefits. It is general information, not medical advice.
Short answer: the best-known trial found people who ended their showers cold took 29% fewer sick days off work, but weren’t ill on fewer days. A 2025 review found no measurable effect on immune function in the hour after cold water. Cleveland Clinic calls the evidence “preliminary.”
The cold shower trial
The study most often cited is a 2016 randomized trial in PLOS One. 3,018 adults in the Netherlands were assigned to finish their usual warm shower with 30, 60, or 90 seconds of cold water every day for 30 days, or to shower as normal.
The cold groups had “a 29% reduction in sickness absence” from work. But “for illness days there was no significant group effect.”
So people were sick about as often. They just called in sick less. The authors’ own conclusion is a “reduction of self-reported sickness absence but not illness days.”
The limits are in the paper. “All outcomes were self-reported.” Participants “could not be blinded,” and “a placebo-effect of this intervention cannot be ruled out.” The cold water averaged about 10 to 12°C.
The endotoxin study
A 2014 study in PNAS trained 12 volunteers for 10 days in meditation, breathing techniques, and cold exposure, including immersion in ice-cold water. Then they and 12 untrained controls were injected with a bacterial toxin that triggers a flu-like reaction.
The trained group had lower levels of inflammatory markers and fewer flu-like symptoms. Here’s what the headline won’t tell you: the training combined three things, and the authors link the effect to adrenaline released while practicing the breathing techniques. The study doesn’t isolate cold water.
What the 2025 review found
| Outcome | 2025 PLOS One review of 11 trials |
|---|---|
| Immune function, immediately after | No significant effect |
| Immune function, 1 hour after | No significant effect |
| Inflammation, immediately and 1 hour after | Higher |
| Longer term | “Narrative synthesis suggested longer-term benefits,” citing the sick-day result above |
Cleveland Clinic lands in the same place: “Evidence is preliminary, but some research suggests cold therapy might support immune system function.”
Plunging when you are sick
None of the sources here test it. What they do say: cold water “raises your blood pressure and forces your heart to work harder” (Cleveland Clinic). With no study to go on, ask your doctor before plunging while you are ill.
Who should check with a doctor first
Cleveland Clinic lists heart disease, high blood pressure, diabetes, pregnancy, peripheral neuropathy, poor circulation, venous stasis, and cold agglutinin disease.
If you want to try the shower version
The trial’s routine costs nothing: end your normal shower with 30 to 90 seconds of the coldest water you have. If you later want a full plunge, an inflatable tub like the Icebound Essentials XL at $549.99 has chiller ports for later.
Bottom line: a cold finish to your shower was linked to fewer sick days off work, not fewer illnesses, and the immune effect hasn’t been measured clearly. Plunge because you like it, not as a cold remedy. For the other claims, see the cold plunge benefits overview linked above.
Sources
- Buijze GA, et al., “The Effect of Cold Showering on Health and Work: A Randomized Controlled Trial,” PLOS One, 2016: journals.plos.org
- Kox M, et al., “Voluntary activation of the sympathetic nervous system and attenuation of the innate immune response in humans,” PNAS, 2014 (abstract): pubmed.ncbi.nlm.nih.gov
- Cain T, et al., “Effects of cold-water immersion on health and wellbeing: A systematic review and meta-analysis,” PLOS One, January 29, 2025: journals.plos.org
- Cleveland Clinic, “Are ‘Cold Plunge’ Ice Baths Good for You?” May 8, 2026: health.clevelandclinic.org
- Icebound Essentials XL listing, checked September 2026