Can You Really Dehydrate or Get Diarrhea by Using an Infrared Sauna?
Yes, using an infrared sauna can certainly cause dehydration if you’re not careful. In fact, dehydration is one of the primary risks of any sauna (infrared or traditional) because you sweat so much. Infrared saunas operate at a gentler temperature than traditional saunas, but they still induce a deep sweat.
During a session, your body can lose a significant amount of water. If you don’t replace those fluids, you can become dehydrated. Signs of mild dehydration include feeling thirsty, dry mouth, headache, dizziness, and fatigue. In a sauna context, you might also notice your heart rate going up more as you get dehydrated (heart beats faster to try to maintain blood pressure).
What Should I Do Before Getting Into a Sauna?
It’s vital to drink water before and after your sauna sessions – and even sip water during the session if it’s longer than 15 minutes. Many experts recommend drinking at least a couple of glasses of water after a sauna to rehydrate. Some people also like to have an electrolyte drink (to replenish sodium, potassium, etc., lost in sweat), especially if they stayed in the sauna for a long time or if they’re on a day when they didn’t eat/drink much beforehand.
If you properly hydrate, an infrared sauna should not dehydrate you to a dangerous extent; however, without adequate fluid intake, dehydration can happen and in severe cases could lead to heat exhaustion or heat stroke. Always listen to your body – if you start feeling lightheaded or overly parched in the sauna, it’s time to get out and cool down with some fluids.
Why Dehydration Matters
Aside from just feeling thirsty, dehydration can have a few consequences. It can lower your blood pressure (since there’s less fluid volume in your blood), which might make you feel faint when you stand up. It also can upset the balance of electrolytes in the body, which can cause symptoms like muscle cramps or, if extreme, heart palpitations. Thus, the emphasis on hydration cannot be overstated.
Remember that alcohol and saunas don’t mix – alcohol dehydrates you further and impairs your body’s cooling mechanisms, dramatically increasing the dehydration and overheating risk. So, avoid drinking alcohol before or during a sauna session. And certain medications (like diuretics or “water pills”) could also predispose you to dehydration in a sauna, so use caution or consult a doctor if you’re on such medications.
Diarrhea is Uncommon but Possible Indirectly
It’s much less common to hear about diarrhea as a direct effect of sauna use, but there are a few ways an infrared sauna session might contribute to an episode of diarrhea in some individuals. First, consider that intense heat and sweating can sometimes have odd effects on the autonomic nervous system (which controls digestion). Some people, after a period of heat stress, find that their digestive tract becomes more active once they cool down – this is somewhat analogous to how exercise can stimulate bowel movements in some. However, it’s not typical for a sauna to directly cause diarrhea.
That being said, one potential link is through dehydration. If you become dehydrated in the sauna and don’t rehydrate properly, the loss of fluids and electrolytes might upset your digestive system. Dehydration can cause electrolyte imbalances that occasionally lead to gastrointestinal disturbances. More commonly, though, dehydration tends to cause constipation rather than diarrhea because your body reabsorbs more water from the colon when you’re low on fluids. So dehydration alone usually doesn’t cause diarrhea – if anything, the opposite.
Another angle is intestinal motility and sauna use: When you’re in a sauna, blood flow is redirected toward your skin to help cool you, and perhaps away from your digestive organs a bit. After the sauna, as your body recovers, there could be a rebound increase in gut activity. Some sauna users anecdotally report needing to use the bathroom (for a bowel movement) after a session, perhaps because the relaxation of the sauna triggers the parasympathetic nervous system (“rest and digest” mode) afterward. This might be a normal bowel movement, not pathological diarrhea.
One more consideration is detoxification reactions. Saunas are often said to help “detox” by eliminating some toxins through sweat. If someone has a lot of toxins or is doing a vigorous detox program that includes saunas, they might experience loose stools as part of the body’s cleansing process. This is more speculative and individual – not a guarantee by any means. It’s sometimes mentioned in holistic health contexts: as your body releases certain substances from tissues, you might get temporary diarrhea or other symptoms. But from a strict medical standpoint, it’s not a direct or expected effect.
There is also emerging research on heat stress and the gut. One study found that intense heat (like sitting in a sauna to the point of losing 2-3% of body weight in sweat) can increase intestinal permeability (sometimes called “leaky gut”). This means the intestines become a bit more porous temporarily. In theory, increased intestinal permeability could lead to gastrointestinal symptoms or make one more prone to an upset stomach. If the gut barrier is more permeable due to heat stress and dehydration, some people might experience cramping or even diarrhea after extreme sauna sessions. However, this would likely only occur if you really pushed the sauna session to an extreme degree (significant dehydration and overheating). For typical moderate sauna use, this isn’t a common worry.
If You Get Diarrhea
Should you experience diarrhea after a sauna session, consider what other factors might be at play. Did you perhaps have something questionable to eat or a minor stomach bug? It could be coincidence. Or were you already a bit dehydrated or overheated, and the sauna tipped it over the edge? The first step would be to rehydrate, not only with water but also with electrolytes because diarrhea itself causes further fluid and electrolyte loss. Taking a break from sauna until you feel better would be wise. If diarrhea is severe or persistent, obviously seek medical advice.
Also note: If you already have a condition that causes diarrhea (like IBS or IBD, or you’re having a bout of gastroenteritis), using a sauna might not be a great idea until you’re recovered. You’re already losing fluids with diarrhea; adding the sweating from a sauna could worsen dehydration. Plus, if your body is fighting an illness (even a mild tummy bug), the stress of a sauna might not be helpful.
Conclusion
Infrared saunas definitely can cause dehydration if you don’t proactively hydrate. Always drink plenty of water and listen to your body – cut sessions short if you feel signs of dehydration. As for diarrhea, it’s not a typical or direct effect, but in certain scenarios sauna use might contribute to a bout of loose stools (particularly via dehydration or in sensitive individuals).
If you find that you consistently get an upset stomach after sauna sessions, try shortening the session and make sure you’re hydrating and cooling down properly. If it still happens, consider consulting a healthcare provider to rule out other issues. Most people, however, will not experience diarrhea from an infrared sauna, whereas mild dehydration is an ever-present risk that’s easily managed by fluid intake.
Related Article: How Long to Use Saunas
References:
Roca Rubio, M. F., Eriksson, U., Brummer, R. J., & König, J. (2021). Sauna dehydration as a new physiological challenge model for intestinal barrier function. Scientific Reports, 11, 15514. https://doi.org/10.1038/s41598-021-94814-0
Medical News Today. (2019). Saunas and health: Risks and benefits. (Highlights dehydration risk and the need to rehydrate after sweating).
