The folk wisdom "sweat it out" is older than modern medicine. But is there any truth to the idea that intentional heat exposure can help when you're fighting a cold or flu? And more importantly — is it safe?
This article looks at what the evidence shows about infrared sauna use during illness, when it might help, and when you should absolutely stay out.
The Science Behind "Sweating It Out"
The human immune response to pathogens includes fever — an intentional rise in core body temperature orchestrated by the hypothalamus. This isn't accidental. Higher temperatures:
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Inhibit viral and bacterial replication (most pathogens have an optimal growth temperature range)
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Accelerate immune cell production and activation
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Enhance the activity of interferon, the body's antiviral protein
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Increase circulation, getting immune cells to sites of infection faster
Infrared sauna creates what researchers call "artificial fever" — a controlled, voluntary rise in core body temperature without the inflammatory pathway that causes pathological fever. This is the mechanistic basis for the immune argument.
What Research Shows About Sauna and Immune Function
Several lines of evidence are relevant:
1. Regular sauna use reduces cold frequency A randomized controlled trial published in the Annals of Medicine found that subjects using sauna 2–3x per week had significantly fewer common cold infections over a 6-month period compared to controls. When they did get sick, illness duration was shorter.
2. Sauna increases white blood cell activity Studies measuring immune markers post-sauna show elevations in white blood cell count, lymphocyte activity, and NK (natural killer) cell activation — all components of the front-line immune response.
3. Heat shock proteins Heat stress triggers production of heat shock proteins (HSPs), which play a role in protein repair, immune signaling, and pathogen response. HSPs are produced by the same mechanisms activated during fever.
When Infrared Sauna May Help During Illness
Early-Stage Cold (Days 1–2)
When symptoms first appear — mild sore throat, slight congestion, early fatigue — the viral load is still relatively low and the immune system is ramping up. Some evidence supports that heat exposure at this stage can stimulate immune activation before the infection fully takes hold.
If you feel up to it:
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Shorter session: 15–20 minutes
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Lower temperature: 110–120°F
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Aggressive hydration before and after
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Rest immediately afterward — don't use sauna as a substitute for sleep
Lingering Recovery (Post-Acute Phase)
After the acute phase passes but fatigue and congestion linger, infrared sauna may help clear respiratory congestion (the warmth and steam effect), reduce lingering muscle aches, and accelerate immune cleanup of viral debris. infrared sauna for muscle recovery
When to Absolutely Skip the Sauna
Active Fever
If you already have a fever above 100°F, do not use the sauna. Your body is already in high-temperature immune mode. Adding exogenous heat creates risk of:
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Hyperthermia (dangerously elevated core temperature)
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Severe dehydration
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Cardiovascular strain (heart rate is already elevated with fever)
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Electrolyte imbalance
Wait until your fever has broken and you're below 99°F for at least 12–24 hours.
Flu (Influenza)
The flu is significantly more systemic than a common cold — higher fever, more pronounced cardiovascular and systemic effects. The risk-benefit ratio is less favorable. If you have the flu:
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Rest is the primary intervention
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Reintroduce sauna only when you're clearly in recovery (day 4–5+)
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Consult your physician if you have heart conditions or other complicating factors
COVID-19
COVID-19 involves complex systemic and cardiovascular effects in some people. While mild COVID may respond similarly to common cold protocols, the variable nature of COVID presentations makes general recommendations difficult. Consult your physician.
Children and Elderly
Extra caution warranted. Thermoregulatory capacity is reduced in young children and older adults, making heat stress more dangerous during illness.
Practical Protocol: Sauna During Early Cold
Session parameters:
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Temperature: 110–120°F (not your normal range)
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Duration: 15–20 minutes maximum
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Cadence: Once daily if feeling well enough; skip if fatigue is severe
Before session:
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Drink 16–20 oz water with electrolytes
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Eat a light snack if you haven't eaten recently
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Have a towel and change of clothes ready
During session:
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Sit quietly; this isn't the time for movement or stretching
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Exit immediately if you feel dizzy, nauseous, or overly fatigued
After session:
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Drink another 16–20 oz water with electrolytes
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Rest — do not exercise or exert yourself
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Sleep if possible; this is when immune work happens
The Infrared Difference During Illness
Infrared saunas have one practical advantage over traditional saunas when sick: lower ambient air temperature. A traditional Finnish sauna at 185°F requires your upper respiratory tract to breathe extremely hot, dry air — uncomfortable and potentially irritating when you already have congestion or a sore throat.
Full-spectrum infrared saunas operate at 120–150°F cabin air temperature. The heat comes from tissue penetration, not hot air — making it significantly more tolerable for someone with respiratory symptoms.
Prevention Is the Better Sauna Story
The stronger case for sauna and immune health isn't treatment — it's prevention. Regular infrared sauna users show consistently better immune metrics: fewer cold infections, shorter illness duration, higher baseline NK cell activity.
Building a 4–5x per week sauna practice is the strongest immune investment, not just sweating through illness reactively.
Peak Saunas: Full-Spectrum for Complete Immune Support
Peak Saunas full-spectrum infrared models include near, mid, and far wavelengths — providing the photobiomodulation benefits of near infrared alongside the deep-tissue circulation benefits of far infrared.
All Peak Saunas come with a limited lifetime warranty and free shipping to the contiguous US.