Claim Check: "Wim Hof Breathing Boosts Immunity"

The claim

Wim Hof breathing is often said to "boost your immune system". The Wim Hof Method combines breathing exercises, cold exposure and meditation. We give no instructions for it, because the breathing studied involves cyclic hyperventilation followed by breath retention, described elsewhere as forced breathing, and these have documented risks. [1][2] Never practice such breathing near water, in a bath, while driving or alone at heights.

Our verdict: promising lab findings, not shown to boost immunity

The best-known finding is a small study in which trained volunteers had a milder inflammatory response to an injected bacterial toxin. [1] That is not the same as being sick less often or having a "boosted" immune system. Evidence label: promising but limited for a laboratory inflammation response in healthy young people; insufficient evidence for infection or illness outcomes.

What the studies found

1. Kox et al. 2014 (randomized, 24 healthy volunteers)

   Anti-inflammatory IL-10 rose faster, pro-inflammatory markers were lower and flu-like symptoms were lower in the trained group. [1]

   What it did: Intervention group trained 10 days in meditation, breathing techniques and cold exposure; the control group was not trained. [1] All were then given bacterial endotoxin through a vein. [1]

2. Zwaag et al. 2022 (randomized, 48 healthy men in the second study)

   Cold training alone did not relevantly change the response; the breathing exercise did, and the combination was strongest. [3]

   What it did: Compared cold exposure training, a breathing exercise, both, or no training before the same endotoxin challenge. [3]

3. Ketelhut et al. 2023 (randomized, 42 people)

   No positive effects on cardiovascular or psychological measures. [4]

   What it did: Compared a 15-day daily Wim Hof program with a control group. [4]

4. Blades et al. 2024 (randomized, 84 women)

   Equivalent improvements in depressive symptoms, anxiety and stress. [5]

   What it did: Compared a Wim Hof-based program with slow-paced breathing. [5]

5. Fox et al. 2025 (404 adults, semi-randomised)

   Greater momentary gains in self-reported energy, clarity and coping after sessions than meditation, but minimal significant between-condition changes in traits. [6]

   What it did: Compared Wim Hof in-person, remote, or meditation over 29 days. [6]

A systematic review of eight trials judged the evidence "promising" for the inflammatory response, with mixed findings for exercise performance. [7] It called for studies in people with inflammatory disorders. [7]

Why this is not "boosting immunity"

• The 2014 paper title describes attenuation, that is, suppression, of the innate immune response. [1] Its authors described a lower response to a toxin. A lower response is not the same as a stronger one.
• The studies used an injected toxin, not real infections. In the sources we read, none tested whether practitioners catch fewer infections.
• Participants were healthy volunteers in small samples, and the Zwaag studies enrolled only men. [3] Those authors described their work as paving the way for clinical trials, not as proof of benefit. [3]
• The 2014 control group was not trained, so it was not a fair match for attention and expectation. [1] One later trial used an active control and found equivalent results. [5]
• A 2018 imaging paper centered on a case study of Wim Hof himself, so it cannot be generalized. [2]
• In the Zwaag work, participants were trained by either the creator of the method or an independent trainer, and the breathing effect on adrenaline did not vary by trainer. [3]

Where to go next

See the full Wim Hof method guide, cold exposure plus breathwork, and the wider claim check on boosting immunity.