If you have a mild cold with no fever, a short, low-temperature sauna session is probably fine, but if you have the flu, a fever, chest congestion, or any sign of a significant infection, you should skip it entirely, because your body is already under stress and adding heat can make things worse.
You're congested. Your joints ache. That scratchy throat tells you something's coming. And you're wondering if a hot sauna session might sweat it out of you.
Fair question. Heat therapy has been used for centuries to deal with illness. But the answer depends on where you are in the sickness timeline, what symptoms you have, and what you're hoping the sauna will actually do.
Let's walk through it.
The short answer
If you have a mild cold with no fever, a short, low-temperature sauna session is probably fine. If you have the flu, a fever, chest congestion, or any sign of a significant infection, skip the sauna.
The difference matters because your body is already working hard to fight off whatever is making you sick. Adding heat stress on top of that can backfire.
What happens to your body when you're sick
When you catch a virus, your immune system kicks into gear. Your body raises its internal temperature (that's a fever) to create an environment that's less hospitable to the pathogen. Your heart rate increases. Your blood vessels dilate. You're already in a state of physiological stress.
A sauna does several of the same things. Core temperature rises. Heart rate can double. Blood flow shifts toward the skin. You're essentially asking your body to handle two simultaneous stressors.
For a mild cold, most people can handle this without problems. For anything more serious, you're asking your body to do double duty when it's already maxed out.
The fever rule
This is the most important distinction. If you have a fever, do not use a sauna.
Your body has already turned up the thermostat. Adding more heat can push your core temperature dangerously high. There's no research supporting the idea that "sweating out" a fever helps anything. It just adds risk.
Take your temperature before considering a sauna session. If it's above 99.5°F (37.5°C), stay home. Rest. Hydrate. Let your body do its job.
What about the "sweat it out" idea?
The concept that sweating helps flush out a virus is persistent but not supported by evidence.
Viruses live inside your cells. Sweating happens through your sweat glands. There is no direct pathway from infected cells to sweat pores. Sweating doesn't "push" a virus out of your body.
What sweating does do is help regulate body temperature through evaporative cooling. That's useful if you're overheated from exercise or a hot environment. It's not a mechanism for clearing an infection.
The one caveat: some research has found that regular sauna use is associated with fewer colds over time. A 2010 study in the European Journal of Epidemiology followed 50 people who either used a sauna or didn't over a six-month period. The sauna group reported significantly fewer colds. But that's about prevention, not treatment. Using a sauna after you're already sick is a different question entirely.
When a sauna might actually help
There are two scenarios where a sauna could be beneficial during a cold.
Symptom relief
The heat and steam can temporarily relieve nasal congestion. Warm air helps loosen mucus. If you're stuffy and uncomfortable, a short session might make you feel better for a while. Just keep it brief.
The early window
Some evidence suggests that if you catch a cold very early—within the first few hours of noticing symptoms—a sauna session might help. A small German study from 1990 found that people who used a sauna at the first sign of a cold had shorter illness duration. But this is old data from a single study. It's not strong enough to build a protocol around.
The risks you need to know
- Dehydration. You're already losing fluids from your body fighting an infection. A sauna accelerates fluid loss through sweat. If you're not meticulously hydrating before, during, and after, you can make yourself worse.
- Dizziness and fainting. Your blood vessels are already dilated from illness. A sauna dilates them further. Blood pressure can drop. Standing up too fast after a session can lead to fainting.
- Spread to others. If you're using a shared sauna at a gym or facility, you're potentially spreading your illness to everyone else. Respiratory viruses spread through droplets and surface contact. A hot, humid environment doesn't kill most viruses. It might help them survive longer.
- Delayed recovery. If your body is diverting energy to manage heat stress, it has less energy available for immune function. This is speculative but biologically plausible.
Practical guidelines if you decide to go ahead
If you have a mild cold, no fever, and you want to try a short session, here's how to do it safely.
- Keep it short. Five to ten minutes max. Not your usual 20-minute session.
- Lower the temperature. Aim for 150°F (65°C) or below. Not your usual 175°F or higher.
- Hydrate before and after. Drink at least 16 ounces of water before entering. Have another 16 ounces ready for when you get out.
- Listen to your body. If you feel worse during the session—more dizzy, more achy, more congested—get out immediately. That's your body telling you it's too much.
- Shower afterward. A cool shower helps bring your core temperature back down and washes off sweat. Don't do an ice bath or extreme cold plunge. That adds another stressor.
- Rest after. The sauna is not a replacement for rest. If anything, it should be followed by more rest.
When to absolutely skip the sauna
Do not use a sauna if any of the following apply:
- You have a fever
- You have the flu (body aches, chills, fatigue, high fever)
- You have chest congestion or difficulty breathing
- You are dehydrated
- You have been vomiting or have diarrhea
- You are taking medications that affect body temperature regulation
- You have a known heart condition and are currently sick
What to do instead
If you're sick and looking for something to help, focus on what actually works.
- Rest. Your immune system functions best when you're not asking your body to do anything else. Sleep is the single most effective thing you can do.
- Hydrate. Water, electrolyte drinks, broth. Your body needs fluid to maintain immune function and clear mucus.
- Honey. A spoonful of honey has been shown in multiple studies to reduce cough frequency and improve sleep quality in people with upper respiratory infections. It's not a cure, but it helps symptoms.
- Saline rinse. Neti pots or saline sprays help clear nasal passages without the risks of heat stress.
- Ibuprofen or acetaminophen. For fever and body aches. Follow the label. Don't exceed recommended doses.
The bottom line
A sauna is not a treatment for colds or flu. It might provide temporary symptom relief for mild congestion. It might help prevent colds if you use it regularly when you're healthy. But once you're sick, the sauna's job is done.
If you have a mild cold and no fever, a short, low-temperature session is unlikely to hurt you. If you have anything more serious, stay home, rest, and let your body do what it evolved to do.
And if you're unsure, err on the side of skipping it. Missing one sauna session won't set back your health. Pushing through when you're sick might.
This information is for educational purposes. If you have specific health concerns or a pre-existing condition, consult your doctor before using a sauna while sick.
Frequently asked questions
Can you use a sauna to sweat out a cold or flu?
There's no evidence that sweating flushes a virus out of your body. Viruses live inside your cells, and there's no direct pathway from infected cells to sweat pores. Sweating helps regulate body temperature, but it isn't a mechanism for clearing an infection.
Can you use a sauna if you have a fever?
No. Your body has already raised its internal temperature to fight the infection, and adding more heat can push your core temperature dangerously high. If your temperature is above 99.5°F (37.5°C), skip the sauna, rest, and hydrate instead.
Does regular sauna use help prevent colds?
Some research suggests an association between regular sauna use and fewer colds over time. A 2010 study in the European Journal of Epidemiology followed 50 people over a six-month period and found the sauna group reported significantly fewer colds. That finding is about prevention when you're healthy, not about treating a cold you already have.
What are the risks of using a sauna when you're sick?
The main risks include dehydration, dizziness, and fainting, since both illness and heat cause blood vessels to dilate and can drop blood pressure. You may also spread a respiratory virus to others in a shared sauna, and diverting energy to manage heat stress could leave less available for immune function.