You know, I've been reading about cold exposure and immunity for years now, and this question still comes up constantly: "Will jumping in ice water make me sick?" It's one of those cultural beliefs that's so deeply embedded, we forget to actually look at what the body is doing.
Andrew Huberman does a beautiful job here unpacking the mechanisms, and what strikes me most is the paradox at the heart of cold exposure. On one hand, regular cold practice—three times a week, consistently—can genuinely boost your immune markers. We're talking about measurable increases in T lymphocytes, interleukin-6, helper cells. The kind of cellular army you want on standby when a virus shows up.
But here's the twist: that same stress response, if you push it too hard or too often, can suppress your immune function. It's classic hormesis. The right dose builds resilience. Too much breaks you down.
What's really happening is a neurochemical cascade. Cold water hits your skin, and your sympathetic nervous system floods you with norepinephrine and epinephrine. In the short term, this is pro-immune. It activates immune cells, primes your defenses. But if you're spiking adrenaline every day, especially late in the day, you're wearing down those same systems.
I love the Wim Hof study Huberman references—the 2014 PNAS paper where they injected people with E. coli endotoxin. Normally, you'd expect fever, vomiting, misery. But the group doing cyclic hyperventilation beforehand? Way fewer symptoms. Not because their immune system "fought harder," but because the adrenaline surge dampened the inflammatory response. Less inflammation, less suffering.
I see this pattern everywhere in the knowledge base. Heat exposure, exercise, fasting—they all follow the same curve. Stress is medicine when you're strong enough to recover from it. When you're already depleted, it's just more depletion.
The environmental piece is crucial too. Cold itself won't give you a cold, but cold, dry air absolutely thins your mucosal barriers. That's your first line of defense—mucus trapping pathogens before they establish infection. Winter air, heated indoor spaces, mouth breathing in the cold—these all create vulnerability. If you're doing cold plunges and then standing outside shivering in dry winter air, mouth open, you're asking for trouble.
So here's my take: Cold exposure is a tool for building resilience, not for proving toughness. Do it regularly when you're healthy. Three times a week, one to five minutes, get out, warm up properly. Hot shower, dry clothes, maybe some hot tea. Don't linger in the cold trying to "build mental fortitude" while your core temperature drops and your immune system struggles.
And if you wake up feeling off—tired, achy, that telltale malaise—skip the plunge. Rest. Let your body do what it's designed to do. Fever exists for a reason. Inflammation exists for a reason. Sometimes the best thing you can do is get out of your own way and let biology work.
The science here is clear: cold can make you stronger, but only if you respect the dose, the timing, and your body's current state. That's not weakness. That's wisdom.