Cold Plunge for Immunity: What the Science Really Says (2026)

As soon as the days get shorter, the same question comes up again and again: does cold plunging make my immune system stronger? The answer isn’t as simple as social media sells it. But it is more interesting.

One of the largest randomised controlled trials ever conducted on cold therapy looked at exactly this question. With 3,018 participants. Here’s what it shows, what it doesn’t show, and how you can use cold therapy meaningfully for your immune health.

The Short, Honest Answer

Regular cold plunging appears to reduce the number of sick days you take off work, but probably not because you get sick less often. More likely, it’s because you feel less slowed down when you do get sick and bounce back to functionality faster. This is an important distinction that gets lost in most wellness articles about cold therapy and immunity.

The science supports: cold therapy can contribute to better immune function, primarily through mechanisms like stress reduction, sleep quality, and sympathetic nervous system adaptation. The science does not support: cold plunging makes you immune to colds. The rest of this article shows what the research actually shows.

The Buijze Study: What 3,018 Participants Tell Us About Cold Plunging and Illness

The most important study on cold therapy and the immune system is a Dutch randomised controlled trial by Buijze et al. (2016, PLOS ONE). 3,018 participants aged 18 to 65 were randomly assigned to four groups:

30 days of ending their shower with 30 seconds of cold water
30 days with 60 seconds of cold
30 days with 90 seconds of cold
Control group: hot showers only

After this, the three intervention groups could continue cold showering at their own discretion for another 60 days.

The headline result:

The cold-showering groups had 29% fewer sickness absence days than the control group (incident rate ratio 0.71, P = 0.003). This is statistically significant and a meaningful effect.

The critical nuance:

The number of illness days was not significantly different between groups. In other words: the cold-showering participants got sick about as often as the control group, but they called in sick less often. That’s a very important distinction.

Possible interpretation: people who cold-shower regularly experience a cold as less limiting, have more energy to push through and go to work anyway, or their symptoms are less severe. The study didn’t directly measure symptom severity, but the asymmetry between illness days and absence days strongly suggests something like this.

Also interesting: the effect was independent of duration. 30 seconds had the same effect as 90 seconds. Quality of life (measured with the SF-36 questionnaire) was also slightly higher in the cold-showering groups after 30 days, though not significantly higher after 90 days.

What “Boosting Your Immune System” Actually Means Scientifically

The phrase “cold plunging boosts your immune system” is common but scientifically problematic. The immune system isn’t a muscle you can simply train. It’s a complex network of cells, organs, and signalling molecules that ideally works in balance. Over-activation can lead to autoimmunity, under-activation to increased infection susceptibility.

What the research actually shows: cold exposure influences several components of the immune response and can shift them toward better regulation. That’s relevant, but it’s not the same as “boosting.” It’s more like modulation and stabilisation than amplification.

How Cold Therapy Affects the Immune System

Sympathetic nervous system and inflammatory response

Kox et al. (2014, PNAS) showed that combining cold exposure, breathing techniques, and meditation enabled trained participants to actively influence their sympathetic nervous system. In the study, participants were injected with endotoxin (an inflammation-inducing substance). The trained participants showed fewer inflammatory symptoms and higher adrenaline levels than the control group.

This is the strongest evidence that cold exposure can modulate inflammatory responses. Important: the study used the Wim Hof Method, which is cold plus breathing plus mental training. The effects can’t be attributed to cold alone.

Stress reduction as an immunological lever

Chronic stress is one of the most consistent drivers of immune dysfunction. Elevated cortisol over time suppresses the activity of T-cells, NK cells, and other immune cells. The Cain et al. (2025, PLOS ONE) meta-analysis of 11 randomised trials confirmed that cold water immersion acutely reduces stress. Multiple studies also suggest that regular cold exposure lowers baseline cortisol reactivity over weeks.

Translation: regular cold plungers tend to have lower stress. Lower stress tends to mean better immune function. This indirect effect is probably one of the most important mechanisms overall.

Better sleep quality

Sleep deprivation and poor sleep quality are among the strongest predictors of infection susceptibility. A well-known study on university students showed that people who regularly slept less than six hours per night were about four times more likely to develop a cold than those who slept seven hours or more.

Chauvineau et al. (2021) showed that cold immersion can deepen sleep architecture and reduce sleep arousals. Anyone who sleeps better through cold plunging has indirectly activated one of the strongest immune system levers available. More on this in our cold plunge and sleep guide.

White blood cells and norepinephrine

Šrámek et al. (2000) documented the massive surge of norepinephrine (530%) and dopamine (250%) during cold water immersion. Norepinephrine briefly increases white blood cell circulation. Over longer time periods, this appears to result in mild activation of various immune cell populations. The data here isn’t as robust as for stress and sleep, but the mechanism is plausible and consistent with the Buijze observations.

What Cold Plunging Will Not Do for Your Immune System

Here it’s important to stay honest. Cold therapy is not a shield against infection. It:

does not prevent you from catching a cold or flu virus when you’re exposed to one
does not replace vaccines, which provide specific protection against particular pathogens
does not fix an immune system weakened by chronic stress, poor nutrition, or sleep deprivation if those factors aren’t also addressed
is not a substitute for medical treatment in active or serious infections

Understanding this lets you use cold therapy sensibly. Hoping for a miracle effect leads to disappointment.

Should I Cold Plunge When I’m Sick?

This is one of the most common questions. The honest answer:

With acute infection, fever, or feeling significantly ill: NO.

Cold exposure strongly activates the sympathetic nervous system and stresses the body short-term. When your body is already fighting an infection, that’s not the moment to add additional stress. Fever is your body’s deliberate elevation of core temperature to make it harder for pathogens to replicate. Cold exposure interferes with this process.

With mild cold symptoms without fever, or in recovery:

Be cautious in your assessment. Some people feel better after a short, mild cold plunge. Others feel worse and prolong their illness. When in doubt: skip the session and only return once you feel completely healthy. A few days off won’t harm your cold adaptation.

Right after recovery:

Ease back in gently. Shorter sessions than usual, less cold, less often. Your tolerance dropped during illness. Plan a few days to return to your normal routine.

Who Benefits Most From Cold Therapy for Immune Support

Not everyone benefits equally. Here’s an honest assessment of who gets the most value:

People who get sick often, especially when stress and poor sleep play a role.
Professionals in stressful office jobs where every sick day counts.
Parents of young children who get sidelined regularly by their kids’ infections.
Athletes in intensive training phases, where the immune system is often temporarily compromised (the “open window” after hard sessions).
People with frequent travel or shift work, whose sleep and stress levels are chronically strained.
Older adults, whose immune systems naturally lose efficiency with age (with medical clearance).

Those who already rarely get sick (low stress, good sleep, stable lifestyle) can still benefit from cold therapy, but the additional effect will be smaller.

How to Use Cold Therapy Effectively for Immune Function

Consistency over months

The Buijze study showed the 29 percent effect only after 90 days of regular practice. Occasional ice baths don’t deliver the effect. The goal is to make cold exposure a daily habit, especially during autumn and winter months.

Even short sessions count

Reminder: Buijze found identical effects at 30, 60, and 90 seconds of cold showering. More isn’t necessarily better. For immune purposes, short, frequent sessions suffice. For ice baths, you don’t need 10-minute sessions for immune effects, 2 to 5 minutes regularly is plenty.

Combine with the other immune factors

Cold therapy works best as part of a broader lifestyle that supports immune function. Specifically: adequate sleep (7 to 9 hours), regular exercise, balanced nutrition with sufficient protein, fruit, and vegetables, vitamin D in winter, stress management, and social connection. Cold therapy amplifies what these basics deliver. It does not replace any of them.

Start before cold season

The ideal entry into an immune-focused cold routine is before the cold season begins, around September. This gives your body the adaptation phase that Kox 2014 and Buijze 2016 describe as a condition for the observed effects.

💡 For the kind of consistency that produces immune effects, you need reliable access to cold water. Anyone commuting to a lake in winter cold or topping up ice for every session gives up earlier. A home ice bath with precise temperature control makes the regular practice realistic that the Buijze effect requires.

Frequently Asked Questions

Does cold plunging make you get sick less often?

The largest study on this (Buijze 2016, n=3,018) showed 29% fewer sickness absence days but no significant reduction in actual illness days. This suggests cold plunging may reduce the severity or perceived impact of infections, but not necessarily their frequency.

Can I cold plunge when I have a cold?

With fever or significant symptoms: no. With mild symptoms and no fever: cautious assessment, when in doubt skip. Only restart once you feel completely healthy, and start with reduced intensity.

How quickly does cold therapy work on the immune system?

Measurable effects from the research show up after about 30 to 90 days of regular practice. Short-term effects (one session, one week) shouldn’t be expected. Consistency matters more than intensity here.

Do cold showers work or does it have to be an ice bath?

For immune effects, the Buijze study shows that brief cold showers are enough to produce the 29 percent effect. Ice baths produce a stronger stimulus and additional effects (stress reduction, sleep, mental resilience), but for pure immune purposes, cold showers are an effective entry point.

Can children cold plunge?

Special precautions apply for children. They have lower thermoregulatory reserves and cool down faster. If at all, only briefly (seconds to a maximum of 1 minute), with supervision, and warm rewarming afterward. For younger children under 12, it’s generally not recommended without pediatric clearance.

Cold plunging for older adults?

Healthy older adults can benefit, but should be especially cautious. Get medical clearance first, particularly with high blood pressure, cardiovascular disease, or diabetes. Shorter sessions, more moderate temperatures, always with company.

The Bottom Line

Cold plunging isn’t a magic shield against colds. But the science supports that regular cold exposure activates several mechanisms associated with better immune function: stress reduction, better sleep quality, sympathetic nervous system modulation, and possibly reduced severity of cold symptoms.

The Buijze study with 3,018 participants is one of the strongest single pieces of evidence we have in all of cold therapy. 29% fewer sick days is a practically very relevant effect, especially during cold season.

Anyone wanting to experience these effects needs consistency over months. That’s significantly easier to achieve when your ice bath is ready at home anytime. The Theralpine Rhone with Chiller Pro or Chiller Lite makes exactly this daily routine realistic: no commute, no ice top-ups, precise temperature, ready for your session every morning or evening.

Get in now and enjoy the cold!