What does regular sauna use do to your immune system?
Regular sauna use produces measurable changes in your immune system, but whether it actually makes you get sick less often has not yet been proven. The signals are positive enough to regard the sauna as part of a healthy lifestyle, but specific health claims are premature.
After a single sauna session, your immune cells already respond in a measurable way: the production of heat shock proteins (protective proteins that help cells recover under stress) increases, along with both pro-inflammatory and anti-inflammatory substances. That may sound contradictory, but it resembles a temporary 'alert mode' of the immune system. People who normally exercise little respond more strongly to such a heat stimulus than people who train regularly.
Only after a series of 10 sauna baths do the number of immune cells and antibody levels also change in a measurable way. Which cells change exactly, and in which direction, also differs between people who do and do not exercise regularly. Whether those changes actually mean you get sick less often has not yet been demonstrated.
In small-scale research (six participants) into mild heat treatment over seven days, the activity of NK cells, a type of immune cell that attacks infected or abnormal cells, increased, and the stress hormone cortisol decreased. That sounds promising, but given the small number of participants these are preliminary signals, not firm conclusions.
The combination of sauna and cold-water swimming produces a more complicated picture. In experienced winter swimmers, the immune system responds differently than in people doing it for the first time: some immune markers decrease in beginners but increase in regular practitioners. Cause and effect cannot be distinguished here.
People who visit the sauna regularly suffer less frequently from respiratory conditions and flu-like complaints, according to a review study from the Mayo Clinic. But this reflects an association, not proof that the sauna is the cause: people who go to the sauna more often may also live more healthily in other ways.
This answer is based on five small studies and one review article. Most human studies had tens of participants or fewer, and one study counted only six. No study demonstrated that people were randomly assigned to a group with or without sauna and then followed for illness outcomes. The measured effects on blood values are real, but whether regular sauna use actually leads to getting sick less often has not yet been shown in controlled research.
Does sauna bathing help against infections?
There are preliminary indications that regular sauna bathing may have a beneficial effect on your immune system, but the evidence is too thin for firm conclusions. If you have joint complaints or an unusual skin condition, discuss it with your doctor before making it a regular habit.
What does alcohol do to your immune system?
Chronic excessive alcohol use weakens your immune system on multiple fronts simultaneously and increases the risk of serious infections. Light to moderate drinking appears less harmful, but offers no demonstrable benefit for your immune system.
Does too little sleep weaken your immune system?
Yes, too little sleep demonstrably weakens your immune system and increases the risk of infections and chronic inflammatory conditions. Seven to nine hours of sleep is the most commonly cited guideline, and vaccinations also work better when you are well rested.
Does your immune system really weaken as you get older?
Your immune system demonstrably weakens with age, but vaccinations remain worthwhile and a good diet can limit further decline.
Does cold showering boost your immune system?
Cold showering produces measurable stimulation of the immune system, but whether it actually makes you less likely to fall ill has not been proven. Until better research is available, there is no harm in doing it if you enjoy it, but do not count on it as protection against infections.
How do I strengthen my weakening immune system?
You can partly support your immune system by correcting measured deficiencies in vitamins and minerals and by making use of vaccines specifically tailored for older adults. More far-reaching options such as experimental inhibitors are not yet safe enough for daily use outside of studies.