There are numerous studies on the benefits of heat therapy for health and longevity.
Effective heat therapy increases your core body temperature, improves cardiovascular health, decreases inflammation, and stimulates your immune system to fight infections and cancer.
In the late 1800s, Dr. William Coley, the Father of Immunotherapy, discovered that some patients’ cancers healed after they developed a high fever, which led him to develop a treatment known as “Coley’s Toxins,” in which patients were injected with dead bacteria to stimulate a fever response, leading to complete remissions of cancer in some cases.
You can achieve benefits similar to a fever response by increasing your core body temperature with heat therapy, a process known as hyperthermia.
For many decades, clinics and wellness centers around the world have used hydrotherapy (hot and cold exposure), “fever baths,” and local and whole-body hyperthermia to treat numerous health conditions, including cancer.
Saunas… So hot right now
Saunas have become hugely popular in recent years for their well-documented health-promoting and longevity effects. A 20-year Finnish study on sauna users found that 4–7 sauna sessions per week reduced cardiovascular disease-related deaths and the risk of death from all causes by roughly 40% compared with once-weekly sauna use. That’s huge!
If saunas are so beneficial, what about hot baths?
Researchers at the University of Oregon published a 2025 study comparing the physiological effects of three heat therapy methods: a traditional sauna, a far infrared sauna, and a hot tub session, leading them to conclude…
“Hot water immersion elicits the greatest thermoregulatory, cardiovascular, and immune responses compared with both sauna modalities.”
Turns out, the most beneficial heat therapy method is also the cheapest. All you need is a bathtub.
Let’s dive in…
The study examined 10 men and 10 women aged 20 to 28 who exercised regularly. Each participant had three heat therapy sessions, one week apart.
#1 Hot water immersion: 45 minutes at 105 degrees (40.5 °C).
#2 Traditional sauna: three 10-minute sessions set at 176 degrees (80 °C) with five-minute breaks. The average temperature measured during the sessions was 150 degrees.
#3 Far infrared sauna: 45 minutes starting at 113 degrees and increasing to 149 degrees (65 °C) by the end of the session. The average temperature measured during the sessions was 113 degrees.
*Traditional saunas use electric, gas, or wood-burning heaters to heat the air. Far infrared saunas use electric far infrared light panels, which heat objects inside the sauna (like your body) rather than the air.
Participants did not consume any medications, supplements, alcohol, or caffeine for 24 hours before the test. They were allowed to drink water during the sessions.
The researchers monitored body temperature, sweat loss, blood pressure, heart rate, cardiac output, and immune cell activity, as well as inflammatory blood markers. Data were collected before, during, and after all heat therapy sessions.
The participants’ core body temperatures were measured before the start and every 5 minutes during the heat session. Cardiac output was measured before, halfway, and at the end of the session. Blood samples were collected before and after. Additional blood samples were collected 24 and 48 hours after the heat sessions.
Big finding #1: The increase in body temperature was greater in a hot bath than in either type of sauna.
A hot bath raised participants’ core body temperature by an average of 1.8 degrees Fahrenheit, more than double that of a traditional sauna. The far infrared sauna did not raise core body temperature at all. This makes sense, as the far infrared sauna sessions did not get as hot and far infrared only penetrates 1.5 inches into the body.
It’s worth noting that the traditional sauna test was three 10-minute sessions with two 5-minute breaks to cool off. Participants’ core body temperature would have risen further if they had not taken breaks, but most people (including yours truly) cannot last 45 minutes in a traditional sauna set to 172 degrees. I typically spend 20 minutes in my traditional barrel sauna set at 175-200 degrees. Some days, even 20 minutes is difficult to endure.
Hot Water vs Hot Air
Hot baths are a more effective form of heat therapy because water is roughly 24 times more heat-conductive than air, allowing rapid heat transfer in hot water and rapid heat loss in cold water. Think about it. 70-degree air feels really nice. 70-degree water, on the other hand, feels “freezing” and can cause hypothermia within a few hours. Longer exposure can lead to death.
Big Finding #2: More sweat loss in a hot bath and a traditional sauna
Researchers measured sweat loss by weighing participants before and after the sessions. The total sweat loss was roughly twice as much in the hot bath and the traditional sauna as in the far infrared sauna. Sweat is one way that your body excretes certain heavy metals and environmental toxins. More sweat loss means more detoxification. Bonus!
Big Finding #3: More cardiovascular benefits from a hot bath
-Cardiac output (heart rate and blood flow) increased the most in a hot bath [+3.7 liters per minute], with no difference between traditional sauna and far infrared saunas.
-The increase in heart rate was similar in the hot bath and the traditional sauna (+34-39 bpm) and higher than in the far infrared sauna (+26 bpm).
-The decrease in mean arterial pressure (blood pressure) was significantly greater in hot water than in either sauna method. Heat makes blood vessels expand.
Big Finding #4: A hot bath was the only therapy to stimulate an immune response
-Interleukin-6 (IL-6) cytokine concentration increased an average of 38%.
-There was a small 2-3% decrease in T helper cells (CD4+).
-Cytotoxic T cells (CD8+) were measured at 32.4% before the heat session and peaked at 34.8% 48 hours after the session.
-Natural Killer cells (CD16+CD56+) increased significantly, with about a 20% increase measured 24 hours after the hot bath and still remained over 10% elevated at the 48-hour mark.
Here’s a quote from the study summarizing the findings:
“The present study is the first to characterize and compare the acute thermoregulatory, cardiovascular, and immune responses to hot water immersion, traditional sauna, and far infrared sauna in young, healthy adults. In agreement with our hypothesis, hot water immersion led to the most robust changes in core temperature, whole body sweat loss, cardiac output, heart rate, stroke volume, and IL-6 production. Hot water immersion also had the largest reduction in systemic vascular resistance and blood pressure. Secondary analyses of immune cell populations revealed a slight change in cytotoxic T cells, helper T cells, and natural killer cells during hot water immersion, but there were no changes observed in both sauna heating modalities. Together, these findings suggest that hot water immersion imposes the most significant thermoregulatory challenge, triggering both cardiovascular strain and an immune response compared with both traditional and far infrared saunas.”
Caveats
This was a small study done on young, healthy, fit people. Older, less healthy people, and cancer patients, etc., may have a harder time with heat sessions this long or this hot. We don’t know what the optimal heat and dose time is. Shorter daily hot baths might be just as effective… Also, even though the far infrared sauna did not produce results as good as a hot bath or traditional sauna, there are benefits of infrared light that were not measured in this study, including reductions in oxidative stress and glucose and increases in ATP.
Hot Baths Boost Interferon
Interferons are signaling proteins (cytokines) that “interfere” with viral replication. When a cell is infected by a virus, it releases interferons before it dies. These proteins sound the alarm:
They bind to receptors on nearby healthy cells and prompt those cells to produce enzymes that block viral reproduction and destroy viral RNA. They also send signals to immune cells, such as natural killer (NK) cells and macrophages, to come fight the infection.
Many types of viruses suppress and delay the interferon response in your body so they can survive longer. The amount of suppression can vary from person to person.
Hyperthermia from hot baths has been shown to increase the number of white blood cells that fight infections and to increase antiviral interferon production by lymphocytes by 10 times in patients whose temperatures were raised to 102.2 Fahrenheit. [Source]
Even raising a person’s body temperature from 98.6 to 100.4 significantly increases the expression of genes involved in innate immunity, interferon response, and antiviral response. [Source]
Boosting interferon early is key for viral infections. This means get into a hot bath and raise your core body temperature as soon as you start to feel like you are coming down with something. Recently, one afternoon, I felt the beginnings of the flu coming on: My energy dropped, and I felt achy and cold, the all-too-familiar precursor of what was to come, a night of fever, chills, and sweating.
I immediately got into a 104-degree bath for 30 minutes. That night I slept well. No chills, no sweating. The next morning, my Whoop tracker showed my skin temperature was elevated by 1.5 degrees above baseline, indicating a slight fever overnight. I felt achy and run down for the next two days, so I rested and took hot baths both days, but that was it. No fever, no chills, no sweating, no coughing, no head cold. On day three, I was back in action. The flu never manifested.
A Hot Bath Cancer Healing Story
When I first read this study, I was reminded of Carol Howard, who used hot bath hyperthermia as part of her protocol to help her heal terminal peritoneal cancer naturally after doctors told her she had two years to live. She started with 10-minute baths and eventually increased her time to 20 minutes at 102 degrees daily for three weeks per month. Watch our interview here. (The hot bath conversation starts at the 13:40 mark.)
Home-Based Hyperthermic Hydrotherapy, aka a Fever Bath
The hot tub session in this study was 105 degrees for 45 minutes. For comparison, most hot tubs are set at 100-102 degrees. Hot tubs have temperature limits. Bathtubs do not. Even if your bath isn’t 105 degrees, and you don’t stay in it for 45 minutes, it’s plausible to assume you will still get benefits.
For example, you could start with a 20-minute hot bath at 100 degrees and gradually increase the heat and duration with each session.
It’s hard to get into a super hot bath. I suggest increasing the heat once you are in the tub. Pull the plug to drain some of the water at the bottom of the tub as you add more hot water. I do this multiple times during my hot bath session.
Generally speaking, once your face starts to sweat, you’re getting into the hyperthermic “benefit zone.” My face usually starts to sweat after about 5 minutes. It’s fine if it takes you longer. Women generally take longer to sweat in the same heat conditions as men. People who are less “fit” also tend to take longer to sweat than those who exercise regularly.
You can use a cold compress on your head and neck, and drink cool water if that helps you stay comfortable. Keep in mind that drinking cool water will prevent you from getting an accurate oral thermometer reading.
I suggest using a tub thermometer to measure the bath temperature. You can also use an oral thermometer to monitor your body temperature during and after the hot bath.
In the hot tub vs. sauna study, the immune-boosting benefits of a single hot bath lasted at least 48 hours, so it makes sense to take a hot bath several times per week. A daily hot bath may amplify the benefits.
BIG DISCLAIMER: Supervision is recommended!
Things could go wrong. You could faint from the heat, pass out in the tub, and drown. You could get dizzy as you get out of the tub, slip and fall, and severely injure yourself. If you are taking medication, there could be additional risks to heat therapy with increased heart rate and low blood pressure, etc. Start small and be cautious, and make sure someone is with you.
When you are ready to get out of the bath, I suggest pulling the plug and sitting in the tub for a few minutes while the water drains to cool down a bit. Take as much time as you need. Get out slowly and carefully. You may feel lightheaded, slightly dizzy, drained, and weak.
Your temperature will stay elevated, and you may continue sweating for up to 30 minutes afterward. You can cool yourself off with a shower if need be. I like to let my body cool down on its own to maximize the benefits. It is suggested to rest for an hour afterward. After about half an hour, my energy returns and I feel normal again.
You can take a hot bath anytime during the day, but an ideal time is in the evening or right before bed, as it can also improve the quality of your sleep.
Hot tub strategies
Traditional hot tubs (aka spas) expose you to high amounts of chlorine, so I suggest avoiding them. A saltwater or mineral-based hot tub is a safer, less toxic option. Chlorine evaporates in about 24 hours, so you can dechlorinate your hot tub (or pool) by removing the chlorine floater or turning the chlorinator off the day before, then turning it back on when you get out.
What about hot showers?
Although showers weren’t studied, I feel fairly confident that a hot shower won’t yield results comparable to a hot bath, since showers don’t fully immerse you in water.
What about bath salts?
Go for it!
Hot baths and heart healthA study published in the journal Heart found that people who took a daily warm or hot bath had a 28% lower risk of cardiovascular disease and a 26% lower risk of stroke, compared with those who didn’t take frequent tub baths, based on data from more than 30,000 people followed for about 20 years. (Source)
A hot bath is beneficial, like exerciseA review of the research found that regular sauna or hot tub bathing can produce health benefits similar to low-to-moderate-intensity aerobic exercise, such as walking, jogging, and cycling, burning a similar number of calories and lowering blood sugar. (Source)
Heat therapy is linked to lower dementia riskThis study followed 2,315 healthy Finnish men aged 42–60 for a median of over 20 years, finding that moderate-to-high-frequency sauna bathing was associated with significantly reduced risks of both dementia and Alzheimer’s disease.
Heat exposure improves mood and reduces depressionThis study found that whole-body hyperthermia showed significantly reduced depression scores in participants.
In conclusion, heat therapy is wonderful and offers numerous health benefits. And I am so excited to report that a hot bath, which is readily available to almost anyone with running water, appears to be the most beneficial.
I still love the dry-heat experience of my traditional barrel sauna and the social aspect of sauna sessions with friends and family, but I am definitely taking more hot baths now.
If anyone needs me, I’ll be in the tub!
www.traditionalhydrotherapy.com
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This Post Has 23 Comments
Such an interesting study! We have a hot tub and love it for the relaxing benefits of it. It’s outside, fresh air (mostly). Intuitively I think most know that a hot bath is relaxing but this hyperthermia is so interesting to think that it can help with cancer! 105 degress is HOT but getting in and out is the only way. Getting dizzy and feeling faint would naturally happen I would think. Thanks for this – fascinating.
I joined square one when I got my cancer diagnosis. I used hot baths as part of my fight with breast cancer naturally. Put a stock tank in front of my bathtub for greater depth. Cut the legs off an old plastic chair so I had a comfortable place to sit and rest my arms. Made sure I had someone with me at all times who took my temp and BP every 5 min. and recorded it. I would get in at 112* and increased to 116* I worked up to body temp of 104+ max. which I maintained for 1 hr. before drying off and going to bed for the night (exhausted) Temp of 105 and I became confused. I was able to have oxygen on throughout. Did this 3 alternate days/week for several months. My “very agressive” cancer didn’t disappear and a year after diagnosisI had surgery to remove it, but there was absolutely no cancer in the sentinel lymph nodes. My oncologist was shocked as I had taken no chemo or radiation.
Thank you ! I’m so grateful to you and all the knowledge you share God bless you.
Thank you for this report & study!! I have for the most part of my live been stimming , lucky that the places I swim have sauna & hot tubs. 20 years straight I was at Golds gym every morning & night to stim. Then taking my hour jumping between hot tubs, cold water in the pool , then back in sauna until that’s to hot back in cold water following another hot tub but always end w cold water & water stretches. A life long pogram I created after a really bad snow ski accident w fractured back. I’m feeling good no surgeries so I believe in this pogram. I could not workout like I did before the accident so I just slowly created the same movements in water ( pool). It’s funny how we now descover the cold punchguess I did them without knowing ? Yes they r cold but I’m addicted to the feeling , the energy, I get from the stimming, hot tub& sauna. It can take a long time to cool down after a few hours in the gym& for sure my face I hot read, & u can see the steam going out the door when I leave the gym. Sad covid hit!!! Many gyms closed, so my membership ended after the 20 years. I used my bathtub, & now I have a hot tub. Missing the poolnothing like jump in & almost forget to breathe because it’s cold!!! But my 100 lbs. body would warm up the water & give me so much energy that I can withstand what’s throw at me . I’m a horticulturist so I need the energy when you doing that kind of hard labor all day , every day for living. I do think about the chlorine I have to put in my hot tub, I only do natural / herbal medicine. Believe my food is my medicine!!! So yes I have a problem w the chlorine. I have been told hot tubs that use salt is not good for you, something about the salt changes form when hot? So i minimize the amount of chlorine I put in my water, sometimes I wonder if I don’t put enough in ? I might create a bacteria bath that isn’t good for me either . So what is the best way about it? I don’t have chlorine boxes I can move before use? I have a weekly routine I have to follow. One day I put 2oz. Enzymes in followed by next day 2oz. Defender to prevent scale formation in the water. The chlorine I put in the tub after each use . My products are from Leisure time . I’m still a little skeptic when it comes to the chemicals? Any one here have a take on that?
Check out chlorine Dioxide for water purification…… It’s also a great forgotten remedy. See theuniversalantidote.com
I’ve wondered about this, but the gas produced by it may not be good? Or maybe diluted it is?
Public hot tubs are disgusting, especially when you see some of the un-showered people getting into them. So I very seldom will use one.
But I do really like steam rooms, especially hot ones. What are the benefits of a hot steam room?
FYI, I have owned a jacuzzi for over 4 decades. About a decade ago, I discovered a company, Clarity Water Products out of California. They have non-chlorine/bromine products that turn your spa or pool into a mineral bath. It is so refreshing to not have to smell those chemicals both while sitting in your spa and on your body. Obviously, you should be showering both before and after entering/exiting the spa, especially if you are using chemicals. I love their products, and I am not associated with the company in any way. Just another option to consider.
Hi! I am curious about the detox benefits? Are those the same between sauna and bathtub?
Very interesting article! Thank you Chris!
However you are not talking about cold plunge… after hot baths or sauna (or in-between heat sessions)
I know it was not the main topic of the study, but maybe you can talk about that in a future article?
As everyone I heard a lot about Wim Hof, but recently saw controversial posts about ice-cold baths… Would love to learn more about it.
I can only speak from personal experience, but my cardiologist said no cold plunges for me because arterial plaque can break off during vasoconstriction, but I’m allowed to do heat therapy to my own tolerance. I’m only 40 with very minimally elevated cholesterol, so I was surprised.
I’m not sure there’s any published evidence that cold plunges cause plaque to break off and increase heart attack risk, but it’s an interesting hypothesis…
Thank you for summarizing all of these findings. With all the focus on saunas of late, it’s interesting to find out that baths (such as easy thing really) are so healthy. Turns out our parents might have been on to something putting us in the tub every night before bed. :-)
Thanks Chris, very interesting article. I stopped getting into a hot tub, because I have a high blood pressure. If I understood correctly this article notes that getting into a hot tub lowers blood pressure. Is that correct? Will like to hear more about heat and high blood pressure.
Love and peace .
Amy
HI Amy. Interestingly, high heat increases your heart rate, but simultaneously lowers blood pressure as arteries expand, as measured in this study.
Awesome article! I will definitely be taking more baths per week! I would LOVE more information on your barrel sauna. I’ve been thinking about building one! Thanks for all you share, Chris!
I have an Almost Heaven brand barrel sauna from mysaunaworld.com
An additional core body temperature raising mechanism that I see was left out ~ menopause. I’m pretty sure my core temp raises to at least 110 degrees during a hot flash. haha! I’m kidding, of course :) But maybe there is a God-given health benefit to all that extra heat we experience? :) It would be nice to be able to say, “This hot flash is great! I’m boosting my immune system, and lowering my stroke and cardiovascular risk without even trying!”
I do think the hot flashes during menopause serve a purpose. Perhaps immune boosting… Even if it is just to induce detoxification through sweating, that’s a good thing!
I wonder about the toxins in my tap water. I don’t have a whole house filter, only Berkey and a shower filter. Won’t your pores be wide open and absorbing all the junk through your skin?
Hello Chris, what about the cold water dips in the sea?
I love cold plunging!
Wonderful to read about the positive affects of heat. I have been doing detox baths weekly to improve my health. I also put Epson Salt and Baking Soda to the water for it’s high PH value to draw out the toxins that I feel have been giving me problems with my health. One I believe to be a cancer and the and the other intestinal problems. It is very relaxing and a time to unwind with meditation . Incense , music and reflection with positive thoughts .
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