Mężczyzna wychodzący z lodowatej wody jeziora zimą, owinięty ręcznikiem

Cold Showers and Immunity: Do You Really Get Sick Less?

"Cold exposure boosts your immune system" is one of the most repeated claims in biohacking — but the newest, largest meta-analysis on the topic shows something more complex: inflammation rises short-term, and immune markers don't budge. There is, though, one real, if surprising, long-term effect. We break down the evidence.

MNMichał NowakAugust 22, 202611 min read

Table of contents

TL;DR — key takeaways

→Where the cold-exposure-boosts-immunity myth comes from
→What the largest available meta-analysis shows
→Fewer sick days isn't the same as fewer infections
→Why inflammation rises instead of falling
→What this means in practice
→When cold exposure can actually hurt
→The practical summary
→Our editorial recommendation

Where the cold-exposure-boosts-immunity myth comes from

In our knowledge-base entry on cold water exposure, we describe how cold triggers a sharp activation of the sympathetic nervous system and a burst of noradrenaline — a physiological fact that's easy to intuitively translate into "the body mobilizes, so immunity goes up." The problem is that mobilizing the nervous system and genuinely improving immune function are two different things, and intuition doesn't always match what the hard data show.

The largest meta-analysis on this topic to date, published in 2025, gives a more precise answer — and it's more interesting than a simple "works" or "doesn't work" split would suggest.

This article assumes basic familiarity with cold water exposure

If you're looking for a general introduction to the mechanism and typical cold-exposure protocols, start with our cold water exposure entry in the knowledge base. Here we focus exclusively on the immunity angle.

What the largest available meta-analysis shows

Effects of cold-water immersion on health and wellbeing: A systematic review and meta-analysis

Strong evidence

Cain T, Brinsley J, Bennett H, Nelson M, Maher C, Singh B · PLoS One · 2025

A systematic review and meta-analysis of 11 randomized trials covering 3,177 healthy adults, with cold water exposure (baths or showers) at 15°C or colder for at least 30 seconds. Inflammatory markers increased immediately after exposure and stayed elevated an hour later, and the meta-analysis found no significant effect on the immune-function measures assessed either immediately or one hour after exposure. Narrative synthesis (not meta-analysis) suggested longer-term benefits, including a 29% reduction in sickness absence among people who regularly took cold showers.

View study

Two different results that are easy to conflate

Strong evidence

This distinction is key: the meta-analysis (the strongest form of evidence in this review) found no improvement in immune function and no reduction in inflammation — if anything, inflammation rose short-term. The suggestion of lower sickness absence comes from narrative synthesis (a descriptive summary of individual studies, not a statistical pooling of their results), which is a weaker form of evidence and shouldn't be treated as equivalent to the meta-analysis's hard result.

Fewer sick days isn't the same as fewer infections

This distinction is crucial and routinely gets lost in oversimplified summaries: the lower sickness absence observed in studies doesn't mean people taking cold showers catch fewer infections. It means they report calling in sick less often — which could be explained by entirely different mechanisms than a direct immune boost.

Myth

Lower sickness absence among cold-shower takers proves that cold exposure strengthens immunity.

Fact

This exact phenomenon was studied earlier too (Buijze et al., 2016), with an identical result: regular cold showers were linked to lower sickness absence, but with no difference in actual infection frequency between groups. This suggests the effect stems from behavioral or psychological factors (e.g., greater tolerance for discomfort, a different threshold for staying home) rather than an actual change in immune system function.

In other words: people who regularly take cold showers don't get sick less often — they more likely just go to work despite mild symptoms, or the practice is linked to other lifestyle traits or mental resilience that themselves influence the decision to call in sick. This distinction matters for anyone counting on cold exposure to actually reduce how often they catch colds.

Why inflammation rises instead of falling

Cold exposure is a physiological stressor — the body responds to it similarly to other forms of acute stress, with a temporary rise in inflammatory markers as part of the natural adaptive response. That's not inherently concerning (a similar pattern of transient inflammation accompanies, say, intense exercise), but it contradicts the popular narrative that "cold dampens inflammation" in the context of a single session.

A time-dependent effect, not an instant one

Moderate evidence

The Cain et al. review highlights that cold exposure effects are time-dependent — some parameters change immediately after exposure, others only hours later (e.g., lowered stress only visible at 12 hours, not earlier). This suggests a single session isn't enough to draw conclusions about "instantly" boosting anything — longer, systematic observation of regular practice is needed.

What this means in practice

What cold showers don't actually do for immunity, per current evidence

They don't measurably increase immune cell activity in the short period after exposure
They don't reduce inflammation immediately after a session — if anything, they temporarily raise it
They have no proven effect on the actual frequency of catching infections (colds, flu)

What cold showers may genuinely offer, per available data

Possibly lower reported sickness absence — likely for behavioral, not immunological, reasons
A drop in subjective stress, visible with a delay (around 12 hours after exposure)
Improved subjective wellbeing and alertness right after a session, described further in our cold water exposure entry

If you practice cold exposure for wellbeing, relaxation, or as part of a hormetic routine — the data support that. If you're doing it specifically to get sick less often, it's worth recalibrating expectations: current evidence doesn't back that particular mechanism.

When cold exposure can actually hurt

Situations that call for caution

People with cardiovascular disease should consult a doctor before starting regular cold exposure, given the sharp cardiovascular response it triggers. Intense, chronic physiological stress (including very frequent, prolonged cold exposure without proper adaptation) could theoretically add further strain to a body already burdened by other stressors — people who are overtrained or chronically sleep-deprived should exercise moderation rather than treat cold exposure as a universal remedy.

The practical summary

Question	Short answer
Do cold showers boost immunity?	No meta-analytic evidence of improvement in measurable immune-function parameters
Do they reduce inflammation?	Not short-term — inflammation temporarily rises after exposure
Do you get sick less often?	Data suggest lower sickness absence, but no difference in actual infection frequency
So where does the lower-absence effect come from?	Likely behavioral/psychological factors, not a direct immune change
What does the data actually support?	A possible delayed drop in stress and improved subjective wellbeing

Cold showers and immunity at a glance

Our editorial recommendation

Cold exposure is a legitimate, potentially valuable practice for wellbeing and relaxation, but "boosting immunity" isn't a mechanism the current best available evidence supports. If your main goal is getting sick less often, it's worth investing time and energy in interventions with sturdier evidence behind them — sleep, physical activity, vaccination — and treating cold exposure as a wellbeing add-on, not an immune strategy.

The biggest risk of popular claims about cold exposure and immunity isn't that the practice is harmful — because it usually isn't — it's that people rely on it instead of interventions with genuinely sturdier evidence, like sleep or vaccination.

Michał Nowak, VitMode editorial team

Frequently asked questions

Most available research, including the latest meta-analysis, covers cold showers and baths under controlled conditions, not winter swimming in open water — there's no solid basis to assume winter swimming has a meaningfully different immune effect than a controlled cold bath at similar temperature and duration.

There's no evidence of such a dose-response relationship for immunity — available studies found no improvement in measurable immune parameters even with regular practice, so there's no basis to assume extending or intensifying sessions would change that result.

There's no evidence cold exposure shortens an already-developed infection, and the added physiological stress during illness could be an unnecessary burden on the body — it's more sensible to hold off on intense cold exposure until you've recovered.

Subjective reports may reflect a placebo effect, general lifestyle improvements accompanying a new, discipline-requiring practice, or the behavioral effect described above (reporting sick less often despite mild symptoms) — none of these mechanisms is the same as an actual strengthened immune response.

Sources

Michał Nowak

MSc in Clinical Dietetics, certified sports-nutrition coach

Michał specializes in metabolic nutrition, intermittent fasting and sports supplementation.

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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.