You’re feeling under the weather, and someone mentions hitting the sauna to “sweat it out.” Sounds tempting, right? But before you crank up the heat, let’s talk about what actually happens when you combine 180°F temperatures with a body that’s already fighting off illness.
After helping hundreds of families set up their home saunas—and using them ourselves through plenty of sniffles and sore throats—we’ve learned a thing or two about when heat therapy helps and when it might make things worse.
This guide breaks down what research actually shows about sauna use during illness, based on multiple studies and decades of Finnish sauna wisdom. You’ll know exactly when to fire up the heater and when to stick with chicken soup instead.
Table of Contents
- The Science: What Actually Happens When You Sauna While Sick
- When Saunas Can Help: Mild Symptoms and Smart Timing
- When to Skip the Sauna: Red Flags and Real Risks
- Traditional vs. Infrared: Which Works Better When You’re Under the Weather?
- The Prevention Game: Building Immunity Before You Get Sick
- Safe Sauna Protocols for Cold and Flu Season
- Your Questions Answered
The Science: What Actually Happens When You Sauna Sick
Let’s start with what we know for sure. When you sit in a sauna at 175-195°F, your body temperature rises by about 2°F and your heart rate jumps to 120-150 beats per minute—similar to moderate exercise. A 2013 study examining sauna effects on white blood cells found that a 15-minute session until core temperature rose by 1.2°C resulted in a statistically significant increase in white blood cell production, particularly in trained athletes.
But here’s where it gets interesting for sick folks. According to research published by the National Institute of Health, “Inducing mild heat-stress through the use of hot springs (balneotherapy), hot baths, saunas, steam-rooms and application of hot mud (pelotherapy), can be used to mimic fever and activate immune defenses.” Your body essentially creates an artificial fever, which sounds helpful—except when you already have a real one.
The research on whether this actually helps during illness is mixed. A randomized controlled trial in Berlin tested whether inhaling hot air (90°C) in a sauna helped with cold symptoms. After studying participants who sat in saunas for three days, researchers found that “participants who had inhaled hot air in the sauna did not show significantly different common cold symptoms compared with participants who had inhaled air at room temperature.”
Translation: The heat alone didn’t cure anyone’s cold. But that doesn’t mean saunas are useless when you’re sick—it’s just more complicated than “sweat equals healing.”
When Saunas Can Help: Mild Symptoms and Smart Timing
Nasal Congestion and Sinus Pressure
If you’re dealing with a stuffy nose but no fever, a sauna session might actually provide relief. The warm, humid air can help loosen mucus and moisten your nasal passages, similar to the relief you get from a hot shower but more intense.
We’ve found that adding water to the rocks (creating löyly) works particularly well for congestion. The steam opens things up without the harsh effects of decongestant medications. Keep sessions to 10-15 minutes and breathe normally through your nose when possible.
Muscle Aches Without Fever
Got those annoying body aches from fighting off a cold? The heat from a sauna can improve blood circulation and ease muscle pain, which might be beneficial when you’re recovering from an illness. Think of it as a full-body heating pad that actually gets deep into the tissue.
The key here is timing. Wait until you’re past the acute phase—no fever, no chills, just residual achiness. A gentle 10-minute session at a lower temperature (around 150-160°F) can help without overtaxing your system.
Stress Relief During Recovery
Being sick is stressful, and stress makes recovery harder. A mild sauna session can trigger your parasympathetic nervous system—the “rest and digest” response that helps your body heal. Just keep it short and sweet.
When to Skip the Sauna: Red Flags and Real Risks
The Fever Factor
This one’s non-negotiable: If you have a fever, your body temperature is already elevated, and adding more heat can be dangerous. Having a fever means your immune system is fighting against infections by raising the body temperature, and an infrared sauna will add further strain to your cardiovascular system and body functions.
We’re talking about real risks here—dehydration, heat exhaustion, even heart strain. Your body’s already working overtime to regulate temperature. Don’t make it work harder.
Active Flu Symptoms
While the common cold and influenza are both caused by respiratory viruses and share some symptoms, the flu is a more serious illness. Influenza often causes a higher, longer-lasting fever. For that reason, it’s best to avoid the sauna if you have the flu.
The flu hits your whole system—high fever, extreme fatigue, body aches that feel like you got hit by a truck. Your body needs rest, not additional stress from heat exposure.
Dehydration Danger Zone
Both illness and sauna use cause fluid loss. The sweating induced by the sauna can cause you to lose more body fluids than usual. Staying hydrated is one of the most important aspects in fighting the common cold or flu, and if your body is losing more fluid than it’s consuming, it could hinder your immune system’s ability to fight the pathogens causing your sickness.
If you’re already struggling to keep fluids down or dealing with any stomach symptoms, skip the sauna entirely. Dehydration will make everything worse.
Respiratory Infections
Those experiencing respiratory illnesses such as bronchitis or pneumonia should avoid sauna use as the heat and steam may worsen symptoms. If you’re having any trouble breathing or chest congestion (not just nasal), the sauna’s probably not your friend right now.
Traditional vs. Infrared: Which Works Better When You’re Under the Weather?
Traditional Saunas (170-195°F)
Traditional saunas heat the air around you, creating that classic Finnish experience. When you’re mildly sick:
Pros:
- Better for congestion relief when you add water to create steam
- Can provide temporary symptom relief for mild colds
- The ritual itself can be psychologically comforting
Cons:
- Higher temperatures mean more cardiovascular stress
- Harder to tolerate when you’re not feeling 100%
- Greater dehydration risk
Infrared Saunas (120-150°F)
Infrared saunas operate at lower temperatures, typically between 120 and 140 degrees Fahrenheit. They use infrared heaters to emit radiant heat that penetrates deeper into the skin without causing excessive surface heat. This gentler warmth can be particularly useful for those who might struggle with high temperatures due to illness. Pros:
- Lower operating temperature is easier to handle when sick
- Can help with muscle aches and joint pain
- Less risk of overheating
Cons:
- The health benefits of infrared saunas have been documented in clinical studies, but the jury is still out on whether saunas are beneficial for treating cold or flu viruses.
- Won’t provide the same steam benefits for congestion
The Prevention Game: Building Immunity Before You Get Sick
Here’s where saunas really shine—prevention. A study of 25 participants who used the sauna one to two times per week for six months compared to 25 controls found significantly fewer episodes of common cold in the sauna group. This was found particularly during the last three months of the study period when the incidence was roughly halved compared to controls.
Notice that timeline? It took three months before the protective effect kicked in. This isn’t a quick fix—it’s a long-term investment in your immune system.
How Regular Sauna Use Boosts Immunity
Regular sauna use has been shown to positively impact the immune system. The elevated body temperature experienced in a sauna mimics a fever, which is the body’s natural defense mechanism against infections. This artificial fever helps to boost the production of white blood cells, improving the body’s ability to fight off pathogens.
The sweet spot seems to be 2-3 sessions per week at 15-20 minutes each. More isn’t necessarily better—consistency matters more than intensity.
Heat Shock Proteins: Your Body’s Repair Crew
Heat shock proteins play a significant role in recovery from sickness and illness. HSPs help to protect the cells and reduce inflammation and promote the natural healing process. Think of them as your body’s maintenance team, fixing cellular damage and keeping everything running smoothly.
Regular sauna use increases heat shock protein production even when you’re healthy, giving you a buffer against future illness.
Safe Sauna Protocols for Cold and Flu Season
If you decide to use the sauna with mild symptoms, here’s how to do it safely:
Before You Go In
- Check your temperature – No sauna with any fever, period
- Hydrate heavily – Drink 16-20 oz of water beforehand
- Eat something small – Low blood sugar plus heat equals trouble
- Start cooler – Set temperature 10-20°F lower than usual
During Your Session
- Keep it short: 10-15 minutes max when sick
- Sit lower: Heat rises, so the lower bench is cooler
- Listen to your body: Any dizziness, nausea, or worsening symptoms means get out immediately
- Breathe normally: No forced breathing exercises when congested
After You’re Done
- Cool down gradually: No cold plunges or showers when sick
- Rehydrate: Another 16-20 oz of water minimum
- Rest: Don’t jump back into activities
- Monitor symptoms: If anything gets worse, you overdid it
Special Considerations for Home Saunas
If you’re using your home sauna while family members are healthy:
- Sauna alone to avoid spreading germs
- Wipe down surfaces with disinfectant after use
- Air out the sauna thoroughly
- Wait until you’re non-contagious (usually 24 hours after fever breaks)
Your Questions Answered
Q: Can I “sweat out” a cold in the sauna? A: While some of the methods used to “sweat out a cold” may provide temporary symptom relief, they don’t shorten the time that you’re sick. You can’t actually sweat out viruses—they’re fought by your immune system, not expelled through pores. The temporary relief comes from improved circulation and congestion clearing, not from eliminating the virus.
Q: How long should I wait after being sick to use the sauna normally? A: Wait at least 24-48 hours after your fever breaks and symptoms significantly improve. Start with shorter, cooler sessions and gradually work back to your normal routine over a week. Your body’s been through a lot—ease back into it.
Q: Is infrared or traditional better for immune support? A: For prevention and regular immune support, both work well. Levels of white blood cells (especially lymphocytes, neutrophils, and basophils) are increased in both trained and non-athletes after sauna use. Choose based on your comfort level and what you’ll actually use consistently. For symptom relief during mild illness, traditional saunas with steam might edge out infrared for congestion relief.
Q: Can kids use the sauna when they have a cold? A: Children aged 6 and above are safe to use a sauna, but should be supervised when doing so. They should spend no longer than 15 minutes in there at one time. However, when kids are sick, it’s best to skip it entirely. Their temperature regulation isn’t as developed, and they dehydrate faster than adults.
Q: What about using the sauna for allergies? A: Studies have shown that the symptoms of eye itching, nasal itching, nasal stuffiness, rhinorrhea and sneezing were all significantly improved during the period of FIR therapy. Unlike with colds or flu, allergies don’t involve fever or infection, so regular sauna use might actually help reduce symptoms.
Q: Should I avoid public saunas when I’m sick? A: Absolutely. You risk infecting others with the virus if you use a public sauna after catching a cold. So stay off public saunas whenever you’re sick with a cold. Or opt for a single-person room. It’s basic courtesy—and many facilities have rules against using their saunas when ill.
The Bottom Line
Saunas aren’t magic cure-alls for colds and flu, but they’re not useless either. The key is timing and common sense. Use them for prevention when you’re healthy, skip them entirely with fever or flu, and consider gentle sessions for mild congestion once you’re on the mend.
The real benefits come from consistent use when you’re healthy—building that immune resilience before cold season hits. Those 2-3 weekly sessions from September through March? That’s your insurance policy against winter bugs.
Your next step depends on your current situation:
- Feeling healthy? Start a regular sauna routine now to build immunity before cold season peaks
- Fighting something off? Check your temperature first, then follow our safe protocols if you’re fever-free with mild symptoms
- Ready to invest in prevention? Visit our showroom for a free sauna session and see how different models might fit your wellness routine
Questions about which sauna setup makes sense for your family’s health goals? Our team can walk you through the options—from compact infrared units perfect for one-person immune-boosting sessions to custom traditional saunas that fit the whole family. Call us at 612-505-9700 or stop by our Cokato showroom.
The information in this guide is for educational purposes and based on general sauna research and our experience in the industry. It’s not medical advice. If you have heart conditions, blood pressure issues, are pregnant, take medications, or have any health concerns, talk to your doctor before using a sauna. Everyone’s heat tolerance is different—always listen to your body and stop if you feel unwell.