Sauna and cold-water therapy · HSA and FSA
Approved by your doctor. Not ours.
Using HSA or FSA funds for a sauna or cold plunge starts with a diagnosis and a doctor who knows you. We collect the published research for your condition and draft the paperwork. Your own doctor, nurse practitioner or physician assistant reviews it and decides.
Find the evidence for a diagnosed condition
Common:Heart failureFibromyalgiaDepressionHigh blood pressureLow back painRheumatoid arthritis
Not only physicians can write the letter. Nurse practitioners, physician assistants and other licensed practitioners often can too. Who can write a letter of medical necessity
Reading our grades
A low grade means the research hasn't been done yet, not that sauna or cold therapy doesn't work. Few heat and cold therapies have had large trials. Grades tell your doctor how much published evidence exists, so they can weigh it with what they know about you. How we grade
For patients
Prepare for the conversation with your doctor
For clinicians
Graded evidence, protocols and letter guidance
Rules and policy
HSA and FSA rules, with a source for every line
Where the evidence is strongest
Graded, cited, and honest about gaps
Fibromyalgia
Randomized trials of mild water-filtered infrared whole-body hyperthermia, a clinic-delivered form of systemic heat, reduced fibromyalgia pain versus multimodal rehabilitation alone and versus sham hyperthermia; in the sham-controlled trial the difference was significant at weeks 4 and 30 but not at week 12, and responder rates did not differ. The only controlled sauna study is small and non-randomized: 12 mild sauna baths raised pressure pain thresholds by 22% versus 8% with exercise-pool sessions. Waon (140 F far-infrared sauna), sauna-plus-aquatic-exercise and hot-water immersion studies also report pain and FIQ improvements, but these were uncontrolled and small (8-44 patients). Sauna-specific randomized data are lacking.
8 studies · reviewed November 8, 2026
Allergic rhinitis
In a small randomized trial of Thai adults with skin-test-confirmed allergic rhinitis, 6 weeks of sauna sessions 3 days per week increased peak nasal inspiratory flow and FEV1 compared with education alone; symptom scores were not reported in the abstract. A second Thai trial randomized 64 patients to steam baths with or without herbs, 30 minutes 3 times a week for 4 weeks; nasal symptoms fell in both groups with no difference between them, but without a no-steam control the trial cannot separate a heat effect from time or expectation. A small Japanese crossover study found that one 10-minute warm mist sauna relieved nasal congestion and increased nasal volume for 30-90 minutes, longer than an ordinary 104 F tub bath; it measured acute effects only.
3 studies · reviewed November 8, 2026
Ankylosing spondylitis / axial spondyloarthritis
In a German randomized trial of 35 inpatients with ankylosing spondylitis, adding six sessions of water-filtered infrared-A whole-body hyperthermia (a clinic radiant-heat device) to physical therapy gave greater pain relief, less analgesic use and improvements in BASDAI and BASFI lasting up to 3-6 months, while HAQ did not change. In a small infrared-sauna pilot, pain and stiffness fell during sessions without increased disease activity. A randomized spa-exercise program that included sauna at one site improved a pooled symptom index at 4 weeks, but sauna's own contribution is unknown. Mechanistic studies report lower pro-inflammatory cytokines after whole-body hyperthermia and no cortisol or lymphocyte change after a single hot bath.
7 studies · reviewed November 8, 2026
Chronic heart failure
Most trials in chronic heart failure tested Waon therapy, a hospital-based protocol developed in Japan: a far-infrared dry sauna at 140 F (60 C) for 15 minutes followed by 30 minutes of blanket rest, given once daily, usually 5 days a week, for 2 to 4 weeks alongside guideline medical therapy. Small randomized and controlled trials (n=30-188), mostly from one Japanese research network, report improvements in NYHA class, BNP, endothelial function, heart rate variability, ventricular ectopy and exercise capacity; a meta-analysis found lower BNP and a small LVEF gain (about 1.5 points). The largest multicenter RCT (WAON-CHF, n=149) did not meet its primary BNP endpoint, though walk distance, cardiothoracic ratio and NYHA class improved more than with medical therapy alone, and its neurohumoral subanalysis found no between-group differences. Outside this setting the evidence is limited to small studies: 140 F sauna in US and HFpEF pilots, single exposures to 176 F Finnish sauna and to warm-water immersion, leg-only heating added to cardiac rehabilitation, a German home hydrotherapy crossover trial, and a small Japanese controlled study in which 2 weeks of half-body hot-spring immersion at 104 F was followed by lower BNP and pulse wave velocity than daily showering.
27 studies · reviewed November 8, 2026
Chronic tension-type headache
In a New Zealand randomized trial, adults with chronic tension-type headache who used a sauna regularly for 8 weeks in addition to advice and education had a greater reduction in headache intensity than those receiving advice alone. Headache duration, sleep, depression and headache disability did not differ between groups. The trial has not been replicated.
1 study · reviewed November 8, 2026
Coronary artery disease (chronic ischemic heart disease)
In the KIHD cohort, more frequent Finnish sauna use was associated with lower risk of sudden cardiac death, fatal coronary heart disease and cardiovascular mortality in a dose-dependent way, and in a Japanese cohort of 30,076 adults almost daily hot-tub bathing was associated with lower incident coronary heart disease; these are associations in general populations, not trials in patients with CAD, and in the KIHD analysis that included women the association was not significant in women alone. In adults with stable CAD, single sauna and warm-footbath sessions acutely improved brachial flow-mediated dilation and coronary flow reserve, but an 8-week randomized trial (4 sessions/week) found no improvement in endothelial function, arterial stiffness or blood pressure. A small non-randomized Japanese study reported improved myocardial perfusion with Waon therapy in chronic total coronary occlusion, and an older German randomized rehabilitation study after bypass surgery found similar LVEF gains with sauna or walking. Older Japanese studies from one group measured invasive hemodynamics during a single 5-minute 107.6 F (42 C) hot-water bath after myocardial infarction: pulmonary arterial and wedge pressures rose during the bath, most in patients with extensive anterior infarction and lower ejection fraction, and both cardiac events that occurred during bathing in a 70-patient series were in patients with lower cardiac function.
14 studies · reviewed November 8, 2026
Essential (primary) hypertension
In the Kuopio Ischaemic Heart Disease (KIHD) cohort, men who used a sauna 4-7 times per week had a lower risk of developing hypertension than men who used it once weekly; this is an association in initially normotensive men. Single sauna or hot-water immersion sessions acutely lower blood pressure in hypertensive patients (including central pressure after an ordinary home bath, without a difference in night-time pressure), but in a randomized crossover trial a single 185-194 F sauna session alone did not lower 24-hour ambulatory pressure; only exercise followed by sauna did. Older uncontrolled and non-randomized German studies reported lower resting pressure after months of regular sauna. Controlled evidence for a sustained effect is limited: an 8-week RCT found lower systolic pressure when sauna was added to exercise in adults with cardiovascular risk factors, while an 8-week sham-controlled RCT of home lower-leg hot-water immersion in hypertensive women found no change in ambulatory pressure. Meta-analyses of heat-therapy trials report modest systolic reductions (about 2-4 mmHg), but the most recent RCT-only meta-analysis found no significant overall effect on systolic or diastolic pressure.
17 studies · reviewed November 8, 2026
Major depressive disorder
Whole-body hyperthermia (raising core temperature to about 101.3 F) and hyperthermic baths have produced rapid reductions in depressive symptoms in some small randomized trials of adults with major depressive disorder. The best-controlled trial used a single session against a credible sham and found a HAM-D advantage that persisted for 6 weeks; secondary analyses of that trial linked response to an acute rise in interleukin-6 (Flux 2023, PMID 37085494; Mac Giollabhui 2024, PMID 38677624). The hot-water bath trials are weaker than they first appear: the sham-controlled trial was significant only with one-sided testing, and the trial against exercise was open label, with its 2-week benefit not significant per protocol or at 8 weeks. A 2025 randomized trial in which both arms also received CBT found large improvements in both the active and sham arms with no added benefit detectable, and a 2019 systematic review of 7 small studies judged the evidence insufficient for general recommendations. Evidence is limited to short follow-up, small samples and mostly medication-free or adjunctive settings. In two analyses of the Japanese JAGES cohort of older adults, daily home tub bathing was associated with fewer new cases of depressive symptoms over 3 and 6 years, significantly in winter; these are associations with screening-scale scores, not trials in diagnosed depression.
9 studies · reviewed November 8, 2026
How we grade evidenceA grade measures how much research exists and how consistent it is. A C or D usually means few trials have been run, not that heat or cold therapy fails. Null results are always shown.Read our editorial standards ›Why your own doctor
A letter is only as good as the doctor behind it
The IRS has warned that a note based on self-reported information does not turn a general-health purchase into a medical expense. So we take the slower route on purpose: the clinician who already treats you, who knows your history and medications, decides whether heat or cold therapy belongs in your care.
SaunaLMN was developed with practicing physicians around what a treating clinician needs to decide: the research for the diagnosis, short and honest, with the limitations left in.
| Letter-at-checkout services | SaunaLMN | |
|---|---|---|
| Who reviews | A clinician you have never met | Your own doctor, NP or PA |
| What they see | A short questionnaire | Your history and the published evidence for your diagnosis |
| How long it takes | Minutes | Your next appointment |
| Who decides | The service's clinician | Your clinician edits our draft, replaces it, or declines |
How it works
Three steps. One decision, and it is your doctor's
- Step 1
Tell us your diagnosis
Pick the condition your clinician has diagnosed and whether you are considering a sauna, a cold plunge or both. Your answers stay in your browser.
- Step 2
Read the evidence
See every study we found for that condition: what was tested, on whom, what happened, and the limits. Including the trials that found nothing.
- Step 3
Take it to your doctor
Print a one-page evidence brief and an optional letter draft. Your doctor, NP or PA edits it, replaces it, or says no.
The rules in brief
What the IRS actually requires
No law or IRS ruling names saunas or cold plunges. The same medical-care test applies to them as to anything else.
- 1It has to treat a specific condition
- The expense must be primarily for diagnosing, treating or preventing a specific disease. In September 2026 the IRS added that, for dual-use items, “a generalized desire to monitor or improve health is not sufficient.”
- 2You would not have bought it otherwise
- Courts ask whether the expense would have been incurred anyway for personal reasons. Be honest with yourself and your doctor about this one.
- 3Built-in saunas are capital expenses
- If it adds value to your home, only the cost above that added value can count, and only for a reasonably basic version.
- 4Mistakes cost real money
- An HSA withdrawal that does not qualify is taxed as income, plus a 20% additional tax if you are under 65. Keep your records.
Latest updates
Policy trackerNovember 5, 2026
2027 health FSA limit set at $3,500September 23, 2026
IRS adds FAQ on dual-use health devicesJune 2, 2026
Law firm announces investigation of questionnaire-based medical-necessity approvalsArticle · updated November 8, 2026
Who can write a letter of medical necessity for a sauna or cold plunge?
For doctors, nurse practitioners and physician assistants
Did a patient bring you a SaunaLMN brief?
Condition-by-condition evidence with PubMed links, the protocols the trials used, contraindications, and a plain description of what a letter of medical necessity has to say. Nothing here asks you to sign.