There's a persistent myth that cold makes you sick. Step into icy water, and your immune system collapses. Shower in freezing temps, catch a cold. It's woven into cultural wisdomâbundle up, stay warm, avoid the chill.
The reality is more nuanced. Deliberate cold exposure, done correctly, doesn't weaken you. It can sharpen your immune response. But timing, context, and understanding the mechanisms matter. Andrew Huberman unpacks the science in this AMA, clarifying when cold strengthens your resilienceâand when it doesn't.
First, the direct answer: No, brief cold exposureâone to ten minutes in cold waterâwill not give you a cold or flu. Viruses and bacteria cause infections, not temperature alone.
The confusion comes from environmental factors. Cold, dry air does increase infection susceptibility, but not because of the cold itself. When you breathe cold, dry airâwhether through your nose or mouthâit dries out the mucosal lining in your nasal passages and throat. That mucus layer is your first line of defense, trapping pathogens before they take hold.
Thinner mucus means weaker protection. This is why winter months, with their dry indoor heating and frigid outdoor air, see higher infection rates. It's not the temperatureâit's the humidity.
If you do cold exposure and then stand outside shivering in dry winter air, mouth breathing, you're giving pathogens an open door. But if you warm up afterwardâhot shower, sauna, bundling upâyou're not creating additional risk.
Here's where it gets interesting. Regular cold exposure can enhance immune function. Not through some mystical mechanism, but through a specific, measurable neurochemical pathway: the release of norepinephrine and epinephrine.
When you immerse yourself in cold water, your body floods with adrenaline. This acute stress response triggers a cascade of immune markersâincreases in interleukin-6, T lymphocytes, T helper cells, and activated B lymphocytes. These are the soldiers of your immune system.
A study on cold-adapted humans found that six weeks of regular cold exposureâthree sessions per week, one hour at 57°F (14°C)âshowed trends toward increased immune cell counts. Not massive spikes, but consistent upward trends. Over time, your body adapts. You become more resilient.
But there's a threshold. Chronic elevation of norepinephrine and epinephrineâespecially late in the day, repeatedlyâcan suppress immune function. It's hormesis: the right dose at the right time builds resilience. Too much, too often, depletes it.
One of the most compelling pieces of research comes from a 2014 PNAS study on cyclic hyperventilationâcommonly called Wim Hof breathing. Participants were injected with E. coli endotoxin, a bacterial agent that induces flu-like symptoms: fever, nausea, vomiting, diarrhea.
Those who performed cyclic hyperventilation before the injection experienced significantly fewer symptoms. Their bodies still encountered the pathogen, but the spike in norepinephrine and epinephrine suppressed the inflammatory immune response that causes those miserable symptoms.
This wasn't the immune system "fighting harder." It was the nervous system dampening the alarm bells. Less inflammation, less suffering. The infection was still there, but the body's overreaction was muted.
Cold exposure works similarly. It activates your sympathetic nervous system, releasing the same neurochemicals that, in acute doses, can modulate immune responses. It's not magicâit's biology.
If you're already sickâtruly sick, with malaise, fatigue, fever, or clear infection symptomsâskip the cold plunge. Your body needs all its energy directed toward recovery, not managing additional stressors.
Cold exposure, like intense exercise or sauna, is a stressor. When you're healthy, stress builds adaptation. When you're already compromised, it drains reserves you can't afford to lose.
If you're feeling slightly offâa minor sniffle, a bit run downâand you still want to do your session, make sure to warm up thoroughly afterward. Hot shower, hot tea, dry clothes, warm environment. Don't linger in the cold.