The Science Behind Sauna’s Effect On Your Immune System
Let’s start with a trivia question: When is your immune system running at max capacity?
Research confirms that your immune system’s performance peaks when your body temperature rises to 103-104 degrees.1
While that answer might surprise you — especially given how much society fears fevers and rushes to medicate them with ibuprofen and tylenol — it’s true! And it’s the reason that sauna bathing, which creates an artificial fever state, is one of the best things you can do for your immune system.
In this article:
- Why Heat + Immune Function Is a Unbeatable Duo
- How Infrared Saunas Boost Immunity
- The Key Advantage of an “Artificial Fever”
- Evidence for Sauna Bathing and Improved Immune Function
- Tips for Sauna Bathing to Boost Immunity
Why Heat + Immune Function Is a Unbeatable Duo
Modern research about heat and immunity2 confirms what the ancient Greeks knew 2,000 years ago: Greek physician Parmenides said, “Give me a chance to create fever, and I will cure any disease.”
Short-term exposure to heat that raises core body temperature (either in the form of a true fever or an artificial one!) creates a unique state of beneficial stress called hormesis.3
And just like the stress of exercise makes our heart and lungs stronger, the stress of heat strengthens our immune system.2 Contrary to what most of us learned in Western societies, fever isn’t the enemy. Fever is actually our body’s way of creating a state of hormesis to eliminate true threats, like viruses or other pathogens.
How Infrared Saunas Boost Immunity
Infrared saunas induce an artificial fever, raising the body’s core temperature 1-4 degrees for a short amount of time.
As the body’s core temperature rises, the body’s immune system responds in some unique ways. Because while the majority of the cells in our body operate at peak capacity at 98.6 degrees Fahrenheit, our immune cells like phagocytes, killer T cells, antibodies, and white blood cells actually work best at 100-104 degrees Fahrenheit.4
That’s why heat from a true or artificial fever is such an effective way of fighting infectious diseases, most of which are severely weakened5 at temperatures above 100 degrees Fahrenheit.
The Key Advantage of an “Artificial Fever”
So, why not just rely on our body’s fever response to fight viruses and other pathogens that pose a threat to our health?
Here’s another question: Have you ever noticed that children get extremely high fevers, while adults rarely do? The part of our brains that controls core body temperature— and triggers a fever response— is called the hypothalamus.
Unfortunately the older we get, the lower our mean body temperature falls and the weaker our fever response becomes.6 Thankfully, the body’s hormetic immune response doesn’t differentiate between a true fever and an artificial fever!
Evidence for Sauna Bathing and Improved Immune Function
The evidence for heat therapy as a powerful immune booster is pretty incredible.
Dr. Nobuhiro Yoshimizu, MD, PhD (former director of the Yokohama General Hospital in Japan) has shown that even a 1% increase in body temperature correlates with a 40% increase in immunity1 as white blood cells, phagocytes, killer-T cells, and lymphocytes operate at peak performance. His research reveals that even cancer cells die at temperatures of 103-104°F, and that the immune benefits of sauna bathing continue even after a heat therapy session ends!1
Numerous studies in Finland (the birthplace of the sauna!) show that baseline immune function improves with sauna bathing. One study7 showed that athletes’ white blood cell count increased immediately after a 15-minute sauna. Another study in Austria found that regular sauna bathers got half as many colds8 as a control group. And yet another study published in the European Journal of Epidemiology showed that regular sauna bathers (twice a week) were 30% less likely to get life-threatening pneumonia.9 Those who upped their sauna sessions to four times a week lowered their risk by 40%!
And in one of the largest studies on heat therapy spanning 20 years, researchers found that people who used a sauna 4-7 times per week were 40% less likely to die from all causes,10 when compared with a control group.
Tips for Sauna Bathing to Boost Immunity
Sauna bathing is one of the best ways you can boost your immune system. Keep the following tips in mind to make the most of your sauna:
- Relax and embrace the heat
Like we talked about earlier, most of us have been taught to fear fevers. But rest assured that you are not at risk for damaging your body. While it’s true that most of the cells in our body are optimized at 98.6°F, those cells can easily weather a core body temperature increase of 1°F-4°F without sustaining damage.2 On the other hand, viruses and other pathogens are significantly weakened at temperatures above 102!
- Hydrate, hydrate, hydrate
You now know that your immune cells are optimized at temperatures of 100°F-104°F. But keep in mind that all of your cells (including those on the frontlines of immune function!) are most effective when they are hydrated. During sauna bathing, you’ll be sweating (aka, losing water). Make sure you are well-hydrated before each session!
- Choose a high-quality sauna
Remember: Your goal is to improve your health and immunity. Don’t settle for cheaper saunas that have an appealing price tag but are built from plywood, off-gas harmful chemicals, and are susceptible to mold. My sauna of choice is the Influence Sauna. Not only is it constructed of high-quality cedar, which won’t mold or off-gas chemicals, but it allows for more flexibility in temperature range (most saunas only reach 150°F, while Influence can heat up to 170°F).
- Work your way up to higher temperatures
I recommend starting at 145° F for up to 45 minutes, and working your way up to 25 minutes at 165° F. If you’re new to sauna bathing, or dealing with health issues, give yourself plenty of time as you work up to higher temperatures. If you feel light-headed or uncomfortable, listen to your body and end your sauna session for the day.
- Talk to your healthcare provider if you’re in a high-risk group
There are a few people who should use a sauna with caution, including anyone who is pregnant, is taking certain medications, has very low blood pressure, hemophilia, or who has had a recent heart attack (which may lead to narrowed arteries). Talk to your functional medicine practitioner before you start sauna bathing!Robyn Openshaw, MSW, is the bestselling author of The Green Smoothies Diet, 12 Steps to Whole Foods, and 2017’s #1 Amazon Bestseller and USA Today Bestseller, Vibe. Learn more about how to make the journey painless, from the nutrient-scarce Standard American Diet, to a whole-foods diet, in her free video masterclass 12 Steps to Whole Foods.
- Yoshimizu, Nobuhiro. The Fourth Treatment for Medical Refugees. Rich Way International, Inc. 2009.
- Evans SS, Repasky EA, Fisher DT. Fever and the thermal regulation of immunity: the immune system feels the heat. Nat Rev Immunol. 2015;15(6):335–349. doi:10.1038/nri3843
- Wiegant FA, Prins HA, Van Wijk R. Postconditioning hormesis put in perspective: an overview of experimental and clinical studies. Dose Response. 2011;9(2):209–224. doi:10.2203/dose-response.10-004.Wiegant
- T. A. Mace, L. Zhong, C. Kilpatrick, E. Zynda, C.-T. Lee, M. Capitano, H. Minderman, E. A. Repasky. Differentiation of CD8+ T cells into effector cells is enhanced by physiological range hyperthermia. Journal of Leukocyte Biology, 2011; 90 (5): 951 DOI: 10.1189/jlb.0511229
- González Plaza JJ, Hulak N, Zhumadilov Z, Akilzhanova A. Fever as an important resource for infectious diseases research. Intractable Rare Dis Res. 2016;5(2):97–102. doi:10.5582/irdr.2016.01009
- El Chakhtoura NG, Bonomo RA, Jump RLP. Influence of Aging and Environment on Presentation of Infection in Older Adults. Infect Dis Clin North Am. 2017;31(4):593–608. doi:10.1016/j.idc.2017.07.017
- Pilch W, Pokora I, Szyguła Z, et al. Effect of a single finnish sauna session on white blood cell profile and cortisol levels in athletes and non-athletes. J Hum Kinet. 2013;39:127–135. Published 2013 Dec 31. doi:10.2478/hukin-2013-0075
- Ernst, E. et al. Regular sauna bathing and the incidence of common colds. Annals of Medicine. 04/1990.
- Kunulsor, SK et al. Sauna bathing reduces the risk of respiratory diseases: a long-term prospective cohort study. European Journal of Epidemiology. 12/2017.
- Laukkanen, Tanjaniina et al. Association Between Sauna Bathing and Fatal Cardiovascular and All-Cause Mortality Events. Jama Internal Medicine. 04/2015.