Wim Hof Method (breathing and cold)
A combination of a specific hyperventilation breathing technique, cold exposure, and mental training that made the cover of a major scientific journal in 2014 because of one genuinely interesting study — and that has since accumulated both overblown marketing claims and a documented, serious drowning risk when practiced incorrectly in water.
Number of studies
2
Safety
Requires caution
Time to effects
Subjective sensations (tingling, lightheadedness, a feeling of euphoria or mental clarity) appear within minutes, even in a first session. Claims of lasting health benefits after weeks or months of regular practice in the average, untrained person are not confirmed in rigorous clinical trials.
Who it's for
Table of contents
TL;DR
A combination of a specific hyperventilation breathing technique, cold exposure, and mental training that made the cover of a major scientific journal in 2014 because of one genuinely interesting study — and that has since accumulated both overblown marketing claims and a documented, serious drowning risk when practiced incorrectly in water.
- →A well-documented, short-term rise in adrenaline during and immediately after the breathing session
- →In one specific study, trained participants showed a blunted pro-inflammatory response and an enhanced anti-inflammatory response to an administered bacterial endotoxin
- →Practitioners subjectively report improved mood, alertness, and a felt sense of stress resilience right after a session
| Type of intervention | Combined protocol: hyperventilation + breath retention + cold exposure + mental training |
|---|---|
| Key study | Kox et al., PNAS 2014 — 24 healthy men, proof-of-principle design |
| Evidence level | Preliminary — one small, specific mechanistic study, not a clinically validated therapy |
| Breathing mechanism | Respiratory alkalosis + transient hypoxia after hyperventilation |
| Most important risk | Documented drowning cases from combining the technique with water — suppresses the natural 'urge to breathe' alarm |
| Status | Biohacking/wellness practice, not a medical intervention; requires caution and should never be combined with water |
Understand
Overview
The Wim Hof Method (WHM), named after the Dutch extreme athlete, combines three distinct elements: a specific breathing technique built on cycles of deep hyperventilation followed by breath retention, controlled cold exposure (cold showers, ice baths, open-water swimming), and a component of mental focus and training. It's this specific combination — not simply taking a cold shower or practicing mindful breathing on their own, each of which has its own separate literature — that this entry covers, in contrast to the general cold exposure discussed in our entry on cold-water immersion.
The method became one of the most recognizable biohacking practices in the world largely because of one specific, genuinely interesting study published in 2014 in the Proceedings of the National Academy of Sciences (PNAS) — one of the most prestigious scientific journals in existence. That paper, by Matthijs Kox and colleagues at Radboud University Medical Center, gave the method a scientific credibility it previously lacked and remains by far its most frequently cited piece of evidence. It's worth stating upfront: this is one study, with a specific and limited design — not proof that 'anyone can consciously switch off their immune system,' a claim that circulates in popular material about the method and goes considerably beyond what the study actually demonstrated.
Alongside the method's growing popularity, especially on social media, reports of serious, sometimes fatal accidents tied to its incorrect use have also grown — above all from combining the hyperventilation technique with being in or under water. This isn't a marginal, theoretical concern — it's a documented, recurring pattern of accidents, covered in more detail further down this entry, that deserves just as much attention as the science behind the method itself.
Practitioners claim that regular use of all three elements leads to better stress tolerance, improved mood, a strengthened immune response, and general 'control' over the autonomic nervous system, traditionally considered entirely involuntary. Some of these claims have a real, if preliminary, basis in the scientific literature — especially regarding short-term, measurable physiological changes during the breathing session itself. Others, especially claims about long-term health benefits in the average, untrained person, remain largely unconfirmed in rigorous clinical research.
A fair assessment of the method hinges on separating three distinct questions that are easy to conflate: does the breathing technique cause measurable, real physiological changes (yes, and this is well described mechanistically); do those changes translate into practical, lasting health benefits for an ordinary person outside tightly controlled research conditions (the evidence here is much weaker and more preliminary); and can the method be practiced safely without any restrictions (no — combining it with water specifically is a documented, life-threatening hazard).
This entry tries to keep those three layers separate: a solidly described physiological mechanism of hyperventilation, the limited and specific evidence from the Kox study, and a real, serious safety risk that anyone considering the method, especially near water, should know about.
History of use
Wim Hof, a Dutch extreme athlete born in 1959, built his reputation on a series of record-setting feats related to cold tolerance — from multi-hour ice immersions to high-altitude climbs in minimal clothing — earning him the nickname 'The Iceman.' From the 2000s onward he began systematizing and teaching his own method combining breathing, cold, and mental training, initially through small, personal workshops. The turning point came in 2011 and 2014, when Dutch researchers at Radboud University agreed to study Hof and a group of participants he had trained under controlled experimental conditions — the result of that collaboration, published in PNAS in 2014, gave the method scientific credibility that went beyond anecdotes and athletic stunts for the first time. Over the following decade the method exploded in popularity through social media, mobile apps, and Hof's own book, while simultaneously accumulating a growing number of media reports and lawsuits tied to accidents, mostly drownings, covered in more detail in the safety section below.
Mechanism of action
The central element of the Wim Hof Method, responsible for most of its measurable physiological effects, is the specific breathing technique: typically 30–40 deep, fast inhales followed by passive exhales, then a breath hold on the exhale (retention) lasting anywhere from tens of seconds to several minutes, with the whole cycle repeated several times. This sequence produces controlled hyperventilation — breathing well beyond the body's momentary metabolic needs — which has two main, well-described physiological effects: respiratory alkalosis and transient hypoxia during the breath-hold phase.
Respiratory alkalosis occurs because fast, deep breathing washes carbon dioxide out of the blood much faster than the body produces it. CO2 functions in the body as an acid (via carbonic acid formation in the blood), so flushing it out excessively raises blood pH above normal. It's this alkalosis, not oxygen deprivation itself, that accounts for the characteristic sensations during the practice — tingling in the extremities and around the mouth, lightheadedness, and in some cases visible muscle spasms (tetany) resulting from altered ionized calcium binding at higher pH. Critically for understanding the risk described later in this entry: respiratory alkalosis suppresses the normal, protective 'urge to breathe' signal, which under ordinary conditions is triggered mainly by rising CO2, not by falling oxygen.
During the breath-hold phase that follows hyperventilation, blood oxygen begins to drop — but, mechanistically crucially, the threshold at which the body would normally send a sharp 'you must breathe now' signal has already been pushed back by the earlier CO2 washout. In other words, hyperventilation extends breath-hold time not by increasing the body's actual oxygen reserves, but by suppressing the natural alarm that would otherwise force a resumption of breathing before oxygen drops to a dangerously low level. This phenomenon is well known to diving physiologists as hyperventilation-induced freediving blackout risk, and it is the direct, mechanistic cause of the safety risk covered in the dedicated section below.
The Kox study found that the breathing technique alone (practiced on land) triggers a sharp, several-fold rise in blood adrenaline (epinephrine) — an effect comparable to acute physiological stress. This elevated adrenaline is the main mechanism by which the trained study participants were able to modulate their immune response to an administered dose of bacterial endotoxin; adrenaline has well-documented anti-inflammatory effects through its influence on cytokine release. Cold exposure, the method's third element, adds its own, separate sympathetic activation and noradrenaline release, similar to the mechanism described in our entry on cold-water immersion — though in the Wim Hof Method it's typically combined with the breathing technique rather than used on its own.
Hyperventilation cycle
30–40 deep, fast inhales and passive exhales wash CO2 out of the blood far faster than the body produces it.
Respiratory alkalosis
Falling CO2 raises blood pH above normal, causing tingling, lightheadedness, and sometimes muscle tetany, while suppressing the normal 'urge to breathe' alarm.
Breath retention on the exhale
After the inhale series, breathing stops — oxygen begins to fall, but the alarm threshold has already been pushed back by the earlier CO2 washout.
Sharp adrenaline rise
The whole sequence triggers a several-fold rise in blood adrenaline, comparable to acute physiological stress.
Modulation of the inflammatory response
Elevated adrenaline suppresses pro-inflammatory cytokine release (TNF-α, IL-6, IL-8) and boosts anti-inflammatory IL-10 — the mechanism demonstrated in the Kox study.
Added sympathetic activation from cold
The accompanying cold exposure contributes its own noradrenaline release, compounding the overall sympathetic activation.
Evidence: early-stage — based on 2 studies in this database.
Benefits
Common myths
MythThe 2014 Kox study proved that anyone can learn to consciously switch off their immune system.
FactThe study involved 24 healthy men, only 12 of whom completed a 10-day intensive training program with Wim Hof himself before being given endotoxin — a specific, selected proof-of-principle protocol, not evidence of a universal, easily accessible ability. The findings are genuinely mechanistically interesting, but generalizing them to 'anyone who practices breathing at home' goes well beyond what the study actually showed.
MythThe breathing technique is entirely safe because it's 'just breathing,' with no substances or equipment involved.
FactHyperventilation physiologically suppresses the natural 'urge to breathe' alarm by washing CO2 out of the blood — this is exactly the mechanism behind documented, real drowning cases among people practicing the technique in water or immediately before submersion. 'No equipment' doesn't mean 'no risk.'
MythThe longer the breath hold, the stronger and better the effect.
FactExtending breath-hold time increases fainting risk in proportion to the depth of the induced hypoxia, without clearly proven additional health benefit beyond the moderate durations used in the Kox study. Longer isn't automatically safer or more effective.
MythSince Wim Hof himself performs extreme feats in and under water, the technique must be safe to practice under those conditions.
FactIt's precisely those stunts and videos showing the technique practiced in water that critics and investigative journalists point to as a source of the misunderstanding behind documented accidents — the method's own instructional material actually warns against practicing it before or during diving, driving, bathing, or swimming, which directly contradicts some of the publicly shown footage.
MythThe Wim Hof Method is essentially the same thing as meditation or mindfulness training under a different name.
FactThe method's mental component has some surface similarities to mindfulness practices, but its physiological mechanism — sharp hyperventilation, respiratory alkalosis, and an adrenaline spike — is fundamentally different from typical meditative techniques, which generally don't rely on deliberately triggering an acute stress response.
MythRegular practice of the method is a way to avoid catching colds and infections.
FactThe Kox study assessed the response to an experimentally administered bacterial endotoxin under tightly controlled clinical conditions, not resistance to real-world viral infections in daily life — a different research model that doesn't automatically translate, and there's no solid clinical evidence that the method reduces how often an average person catches a cold.
Forms & variants
Wim Hof Method (breathing and cold) comes in several forms that differ in bioavailability and use case — the form you pick genuinely matters for how effective the supplementation is.
Breathing technique alone (no cold)
Hyperventilation and breath-retention cycles practiced on their own, without accompanying cold exposure — the most common way beginners are introduced to the method.
Best for: People starting out who want to experience the effects of the breathing technique alone first
Full protocol (breathing + cold)
The breathing technique followed by a cold shower or brief immersion — the complete, original version of the method.
Best for: Experienced practitioners who have already mastered the breathing technique on land
Open-water swimming with method elements
Longer immersion in very cold water (e.g. a natural body of water) combined with breathing-technique elements performed before, not during, the immersion.
Best for: Advanced practitioners experienced with cold exposure, strictly maintaining the rule of never hyperventilating in water
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Practice
Frequently asked questions
One specific study (Kox et al., PNAS 2014) found that trained participants could modulate their inflammatory response to an experimentally administered bacterial endotoxin — a real, measurable effect, but under tightly controlled clinical conditions in a small, selected group (24 people, 12 after training). It is not proof that the method protects against real-world viral infections in daily life for an average person — that's a different research question that this study didn't test.
No — this is the single most important warning about this method. Hyperventilation suppresses the natural, protective 'urge to breathe' alarm, which has been documented in numerous reported drowning cases among people practicing the technique in water or immediately before submersion. The breathing technique should be practiced exclusively on land, in a safe position, never combined with any form of being in water.
This is a typical, expected effect of respiratory alkalosis — hyperventilation flushes carbon dioxide out of the blood faster than the body produces it, raising blood pH, which alters ionized calcium binding and causes the characteristic tingling, sometimes with muscle cramps. It's an unpleasant but usually harmless effect on land — it only becomes dangerous combined with water or with very prolonged, forced hyperventilation.
The exact number is hard to pin down and varies between sources — investigative journalist Scott Carney, a prominent critic of the method, has cited figures ranging from a dozen to more than thirty reported cases in different publications; counting methodology isn't standardized, and most cases lack an independently verified coroner's finding directly linking the death to the technique. Regardless of the exact number, the pattern itself appears real and recurring: drownings among people practicing hyperventilation in water or immediately before submersion, which has also been the subject of lawsuits against Wim Hof's organization.
Not without prior medical consultation. The sharp sympathetic activation and adrenaline spike triggered by the breathing technique, combined with the additional sympathetic activation from cold exposure, may place significant strain on the cardiovascular system, especially in people with undiagnosed or uncontrolled heart disease.
Cold exposure alone (covered in our entry on cold-water immersion) triggers sympathetic activation and noradrenaline release through direct thermal shock. The Wim Hof Method adds a separate mechanism on top of that — hyperventilation and respiratory alkalosis from the breathing technique — which has its own effect profile and, importantly, its own specific risk profile unrelated to the cold itself.
Some adaptation is possible, but extending breath-hold duration increases the depth of hypoxia and fainting risk regardless of experience level — experienced practitioners aren't immune to fainting, which is in fact the cause of many documented accidents among people with years of practice. It's safer to treat every session with the same caution about setting (never in water, always in a safe position) regardless of how long you've been practicing.
Dosage & timing
Typical dose
Typical research and training protocol: 3–4 cycles of 30–40 deep inhales/exhales, each followed by a breath hold on the exhale lasting tens of seconds to a few minutes, practiced on an empty stomach, sitting or lying down, on land, never in water
Form
An equipment-free breathing technique; the cold component is usually a cold shower or brief immersion
This information is for educational purposes and reflects protocols used in research; it is not a substitute for individual medical advice.
Best times to take it
- Always on land, in a safe, controlled setting, never in water, underwater, or immediately before submersion
- Ideally on an empty stomach or at least 2 hours after eating, in a position from which you'd fall safely if you fainted (sitting or lying down, not standing)
- With someone nearby for your first attempts, especially with longer breath holds
- Never before driving, working at height, or any other activity requiring full concentration
What to combine with
Good combinations
Cold Plunges and Cold Exposure — The Wim Hof Method pairs the breathing technique with cold exposure, which is also practiced on its own as a separate practice
Safety
Side effects & contraindications
Possible side effects
Lightheadedness, tingling in the extremities and around the mouth, and muscle tetany — direct, expected effects of respiratory alkalosis
Fainting (loss of consciousness) during or after the breath-retention phase — a documented, non-marginal risk, especially for inexperienced practitioners or overly long hyperventilation
The most serious, real risk: drowning when the breathing technique is practiced in water or immediately before submersion — respiratory alkalosis suppresses the natural 'urge to breathe' alarm, allowing loss of consciousness underwater without the warning signals that would normally force someone to surface
Risk of hypothermia and cold-related injury from uncontrolled, excessively long exposure
Possible cardiovascular risk from the sharp sympathetic activation in people with undiagnosed heart disease
Headache and a feeling of detachment or euphoria after a session, reported by some practitioners, mechanistically consistent with hyperventilation effects described in other medical contexts
Worsened symptoms in people prone to panic attacks, in whom hyperventilation can intensify rather than relieve anxiety
Contraindications
Practicing the breathing technique in water, underwater, or immediately before submersion — an absolute contraindication, directly tied to the documented drowning cases described in this entry
Cardiovascular disease, heart rhythm disorders, uncontrolled hypertension — requires medical consultation before starting
Epilepsy and other seizure-prone neurological conditions — hyperventilation and hypoxia can act as a trigger
Pregnancy
Active respiratory disease flare-ups
A history of fainting or loss of consciousness under similar circumstances
Driving, operating machinery, or any activity requiring full alertness immediately after a breathing session, given the possible dizziness and reduced concentration
Interactions
Medications affecting heart rhythm or blood pressure — the sharp sympathetic activation triggered by the technique may intensify or interfere with their effects; consult a doctor
Anti-seizure medication and conditions lowering the seizure threshold — hyperventilation and hypoxia may theoretically raise seizure risk
Is it worth taking?
Who it's for
- Healthy people without cardiac or neurological contraindications interested in subjective well-being and stress-tolerance benefits
- People already practicing cold exposure who want to add a breathing component — strictly on land
- People interested in the science of hyperventilation and immune response as an interesting, if limited, area of research
Not for
- Practicing the breathing technique in water, underwater, or immediately before submersion — an absolute contraindication, directly tied to the documented drowning cases described in this entry
- Cardiovascular disease, heart rhythm disorders, uncontrolled hypertension — requires medical consultation before starting
- Epilepsy and other seizure-prone neurological conditions — hyperventilation and hypoxia can act as a trigger
- Pregnancy
- Active respiratory disease flare-ups
- A history of fainting or loss of consciousness under similar circumstances
- Driving, operating machinery, or any activity requiring full alertness immediately after a breathing session, given the possible dizziness and reduced concentration
Evidence
Worth knowing
The Kox et al. study (PNAS, 2014) involved only 24 healthy men, of whom 12 completed a 10-day training program before the test.
Respiratory alkalosis from hyperventilation suppresses the natural 'urge to breathe' alarm — the mechanism behind the drowning risk.
Investigative journalist Scott Carney, a critic of the method, has documented numerous reported deaths linked to practicing it in water, though the exact, independently verified count varies between sources.
The method's own instructional materials warn against practicing the technique before or during swimming, diving, or bathing.
Blood adrenaline in trained study participants rose several-fold during the breathing technique.
The method's cold component shares a mechanism (sympathetic activation, noradrenaline release) with standalone cold-water exposure, described in our entry on cold-water immersion.
Studies
In trained participants, plasma adrenaline rose significantly more than in controls, and the pro-inflammatory response to administered endotoxin (TNF-α, IL-6, IL-8) was markedly blunted, while anti-inflammatory IL-10 rose faster.
Kox M et al., PNAS, 2014
Voluntary activation of the sympathetic nervous system and attenuation of the innate immune response in humans
Early-stage evidenceKox M, van Eijk LT, Zwaag J, van den Wildenberg J, Sweep FC, van der Hoeven JG, Pickkers P · Proceedings of the National Academy of Sciences (PNAS) · 2014
A proof-of-principle study in 24 healthy men: 12 underwent a 10-day training program in the breathing technique, cold exposure, and meditation under Wim Hof's guidance; 12 served as untrained controls. After all participants received a low dose of E. coli bacterial endotoxin, the trained group (practicing the technique during the endotoxin challenge) showed significantly higher adrenaline, a stronger anti-inflammatory IL-10 response, and a blunted pro-inflammatory response (TNF-α, IL-6, IL-8) compared to controls, with milder accompanying flu-like symptoms.
View studyThe physiology and pathophysiology of human breath-hold diving
Moderate evidenceLindholm P, Lundgren CE · Journal of Applied Physiology · 2009
A brief overview of the physiology and pathophysiology of human breath-hold diving. The authors note that mortality is concentrated among less well-trained recreational divers who fall victim to hypoxia — relevant context for the safety of any practice that combines breath-holding with being in water, including exercises similar to the Wim Hof method.
View studySources & bibliography
- Kox et al. 2014 — PNAS
- Live Science — 'Gambling with your life': Experts weigh in on dangers of the Wim Hof method
- Dutch News — 'Iceman' Wim Hof cleared of causing death of American teenager (court reporting, 2024)
- Wim Hof Method — official safety guidelines
The PubMed identifiers in this knowledge base were checked against NCBI records (October 2026). If you spot an error in a source, please let us know via the contact form.
Compare with similar entries
About the authors of this entry
Author
dr Piotr ZielińskiEndocrinologist
Piotr has practiced endocrinology for more than fifteen years, mostly in male hormonal disorders and metabolic health. He joined VitMode as a scientific consultant because, as he jokes, he got tired of explaining the same testosterone questions at every appointment and decided to write the answers down properly, once. He reviews content on hormone therapy, supplement pharmacology and drug interactions, making sure articles never turn into encouragement to self-supplement in situations that genuinely need diagnostics and medical supervision. His professional motto — "evidence first, enthusiasm second" — has come up more than once with a patient who arrived with a supplement plan they found online.
297 publications on this site
Medical review
dr Anna KowalczykEditor-in-Chief, Molecular Biology
Anna studied molecular biology at the University of Warsaw, then spent eight years after her PhD in a lab researching the mechanisms of cellular aging and autophagy. She stumbled into science journalism almost by accident — frustrated by how easily her field's findings get oversimplified in the media, she started a blog explaining the biology of aging in plain language. That blog became the seed of VitMode. Today Anna oversees the entire editorial process, holding every piece to the same rigor her old lab demanded: primary sources, methodology checks, and honesty about the limits of the evidence. Outside work, she's a dedicated boulderer.
227 publications on this site
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Comments (2)
- KW
Kasia W. 2 weeks ago
Very clearly explained, especially the interactions section — I hadn't seen it laid out this well anywhere else.
- MT
Marek T. a month ago
Are you planning to update this with the newest study from this year? I saw an interesting meta-analysis.