Far Infrared, Heat Exposure, and Persistent Post-Concussion Symptoms
An Absent Evidence Base, the Treatment Context It Should Be Read Against, and Symptom-Provocation Cautions
Overview
We did not identify a controlled trial of far infrared (FIR) sauna, FIR devices, or whole-body hyperthermia in post-concussion syndrome (PCS; increasingly termed persistent post-concussion symptoms, PPCS), and we did not identify a FIR-specific study in an animal model of concussion or TBI.
This review complements the companion TBI review by focusing on the persistent-symptom population: it states the evidence gap, summarizes the treatment evidence against which any heat-based adjunct should be positioned, and addresses the clinically relevant concern that exertional and autonomic provocation of symptoms in this group makes heat tolerance an open question.
Absence of identified studies reflects the searches conducted here, not a systematic review.
Terminology and Epidemiology
PPCS is described as symptoms lasting weeks to months beyond the expected recovery window, including headache, dizziness, fatigue, impaired concentration and memory, sleep disturbance, mood change, and light and noise sensitivity (Barrow Neurological Institute patient information).
Published estimates of persistence vary widely: 14–36% of acute mTBI cases in one fNIRS study (Hocke et al. 2018, J Neurotrauma 35(11):1224–1232), 10–25% of concussions in a 2024 pilot report (PMC11273594), and higher figures in other trial protocols, reflecting differences in definition and population.
The pathogenesis is described as unclear; a proposed functional overlay model characterizes persistent PCS as having subjective, nonspecific symptoms with undefined underlying pathophysiology and suggests that CBT, neurofeedback, and physical exercise can target treatment (PMC10377031). Some authors prefer “post-TBI syndrome,” since the picture can follow more severe injury.
Direct Evidence for FIR
None identified in humans or in concussion/TBI animal models. FIR-specific preclinical work in other brain injury and disease models (rat ischemic stroke; transgenic Alzheimer's mice, with two positive and one null cognitive result) is reviewed in the companion TBI and Alzheimer's reviews and does not address concussion.
Terminology note: “near-infrared” appears throughout PCS research as a measurement technology (functional near-infrared spectroscopy, fNIRS, used to assess cortical connectivity and as a response biomarker in trials of other interventions) and not as a therapy; those studies are not evidence for infrared treatment.
Treatment Context: What Has Evidence in Adults With PPCS
Sub-symptom threshold aerobic exercise (SSTAE), exercise at an intensity that does not increase symptoms, has the most developed trial evidence for adult PPCS.
In a randomized, single-blind trial of 81 adults aged 18–59 with PCS and exercise intolerance 3 to 24 months after mTBI, SSTAE plus treatment-as-usual versus treatment-as-usual with general exercise advice produced no between-group differences in the primary outcome (Rivermead Post-Concussion Symptoms Questionnaire) at 12 weeks or 6 months, but significantly improved the Buffalo Concussion Treadmill Test symptom threshold at 12 weeks, sustained at 6 months; the SSTAE group's threshold rose from 136 to 158 bpm versus 147 bpm in controls, and the intervention was safe and well tolerated (Valaas et al., Phys Ther 2026;106(6):pzag049).
The ACTBI randomized trial of a 6-week sub-symptom threshold aerobic protocol versus stretching reported preliminary support for prescribing aerobic exercise to adults with PPCS, with quality-of-life benefits despite exercise intolerance (ACTBI, Arch Phys Med Rehabil).
A systematic review of nonpharmacological treatments, as summarized in the Valaas paper, rates the evidence for graded exercise as low to moderate certainty.
This context matters for positioning: any FIR or heat-based adjunct is being offered against an active, clinician-guided treatment with trial evidence, and should not displace it.
Heat Physiology in PPCS
Exercise intolerance, the exacerbation or reappearance of post-concussive symptoms during exercise, was present in 81% of 100 adults 3–24 months after mTBI with persistent symptoms on the Buffalo Concussion Treadmill Test (PMC12604302).
Its pathophysiology is poorly understood but may relate to altered cerebral blood flow response to exercise and/or autonomic cardiovascular dysfunction resulting from the injury or from deconditioning (PMC12159307); autonomic dysfunction after mTBI is described as a major contributor to symptomatology (see the companion TBI review).
Passive heat exposure is a cardiovascular and thermoregulatory stressor that differs from exercise (no metabolic heat production from muscular work), and we did not identify any study of heat tolerance, passive heating, or sauna exposure in PPCS or in post-concussive exercise intolerance. Whether exertional intolerance predicts heat intolerance is unknown.
Symptom Domains: Where FIR Is Marketed and What Is Known
| Domain | Model / Context | Finding | Tier |
|---|---|---|---|
| Headache | PCS population: no FIR data | Headache was the most common adverse event (13/15 heated) in a strong WBH trial in depression (Mason 2025) | No PCS Data; Caution |
| Dizziness / balance | PCS population: no FIR data | Heat-induced vasodilation and postural hypotension are general fall concerns; autonomic dysfunction described after mTBI | No PCS Data; Caution |
| Fatigue | PCS population: no FIR data | No trial identified | Absent |
| Sleep | General-population heat/FIR literature | See companion Sleep review; not studied in PCS | Adjacent Only |
| Mood and anxiety | WBH trials in MDD | See companion Depression and Anxiety reviews; GAD-7 showed no meaningful change in one WBH feasibility study; not studied in PCS | Adjacent, Mixed |
| Cognition / brain fog | FIR in AD and stroke rodent models | Preclinical only; mixed in AD mice; no concussion model identified | Absent for PCS |
On smaller screens, swipe horizontally to view the full table.
Mechanistic Rationale — Transferred, Not Direct
Any rationale for FIR in PPCS rests on transferred, preclinical findings (cytoprotective and anti-inflammatory signaling, mitochondrial effects in rodent stroke and Alzheimer's models) and on general heat-physiology hypotheses.
None has been tested in concussion or PPCS. Because PPCS pathophysiology is itself undefined, a mechanism-first argument is premature in either direction.
Correcting Circulating Claims — Practitioner Advisory
What Patients May Bring
- Wellness and vendor content presenting infrared sauna or devices for post-concussion symptoms such as “brain fog,” headaches, or fatigue. We identified no PCS-specific FIR or infrared-sauna trial behind such statements.
- Red/near-infrared transcranial LED reports in chronic TBI (uncontrolled) or fNIRS research cited as support. The former is a different modality and design; the latter is a measurement tool.
- Generalized “brain” claims from Alzheimer's mouse studies, which are themselves mixed on cognition.
Safety Considerations
Clinical Cautions
- Recent concussion or worsening symptoms: heat exposure should not be introduced; evaluation and standard care come first.
- Symptom provocation: patients whose symptoms flare with heat, hot environments, or exertion should treat this as clinically meaningful. The principle underlying SSTAE, keeping stimulus below the symptom threshold, is a reasonable precaution to extend to heat, but no study has tested heat that way and no heat protocol is offered here.
- Headache and migraine: relevant given headache was the most common adverse event in a strong WBH trial (a different population and much higher heat dose than conventional FIR sessions).
- Dizziness, balance impairment, and orthostatic symptoms: supervised entry, seating, exit, and slow standing advisable.
- Seizure risk: patients with post-traumatic seizures or epilepsy should consult their neurologist; a wIRA-WBH trial protocol lists epilepsy among its hyperthermia contraindications (NCT06204458), a trial-design signal, not a PCS finding.
- Mood: PPCS commonly includes mood symptoms; suicidality warrants standard clinical assessment and crisis resources (in the US, call or text 988) before any adjunct discussion.
- Medications affecting sweating, blood pressure, or alertness should be reviewed before heat exposure. See companion reviews on cardiovascular, conduction disease, Parkinson's, and HPA axis/autonomic function where applicable.
- No claim in this document should be represented to patients as evidence that FIR treats, shortens, or prevents persistence of post-concussion symptoms.
Evidence Grading Summary
| Domain | Model / Context | Finding | Tier |
|---|---|---|---|
| FIR sauna / devices, human PCS | N/A | No trial identified | Absent |
| FIR, animal concussion/TBI models | N/A | None identified in searches conducted | Absent (search-limited) |
| Heat tolerance in PPCS or exercise intolerance | N/A | No study identified | Absent |
| SSTAE, adults with PPCS (not FIR) | RCT, n=81; ACTBI RCT | Symptom threshold improved, primary symptom score unchanged; preliminary QoL support | Context: Active Treatment Evidence |
| Exercise intolerance, autonomic dysfunction in PPCS | Observational | 81% intolerance (n=100); mechanisms unclear | Recognized Concern, Limited Data |
| FIR in rodent stroke / Alzheimer's models | Different injury and disease | Positive (stroke); mixed (AD) | Adjacent Preclinical |
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Clinical Positioning
FIR sauna and FIR-emitting devices should not be presented as a treatment for post-concussion syndrome.
For patients who ask, the most useful content is to direct them to evaluation and the treatments with trial evidence (including clinician-guided sub-symptom threshold exercise), and, if a patient still elects gentle heat, to confirm that symptoms are stable, screen for seizures and medication effects, and frame any use as a supervised comfort choice that is stopped at the first symptom flare.
References
Valaas LJV, Soberg HL, Rasmussen MS, Steenstrup SE, Brunborg C, Røe C, Kleffelgård I. Effects of Sub-Symptom Threshold Aerobic Exercise on Persistent Postconcussion Symptom Burden and Exercise Intolerance: A Randomized Controlled Trial. Phys Ther 2026;106(6):pzag049.
Effect of Aerobic Exercise on Symptom Burden and Quality of Life in Adults With Persisting Post-concussive Symptoms: The ACTBI Randomized Controlled Trial. Arch Phys Med Rehabil. Protocol: PMC7003424.
Exploring exercise intolerance in adult patients with persistent post-concussion symptoms after mild traumatic brain injury. PMC12604302.
Altered autonomic cardiovascular function in adults with persisting post-concussive symptoms and exercise intolerance. PMC12159307.
Hocke LM, Duszynski CC, Debert CT, Dleikan D, Dunn JF. Reduced Functional Connectivity in Adults with Persistent Post-Concussion Symptoms: A Functional Near-Infrared Spectroscopy Study. J Neurotrauma 2018;35(11):1224–1232. doi:10.1089/neu.2017.5365.
Nature-Based Therapeutic Intervention for Individuals with Post-Concussion Symptoms. PMC11273594.
Functional Overlay Model of Persistent Post-Concussion Syndrome. PMC10377031.
Persistent Post-Concussion Symptoms — Diagnosis and Treatment. Barrow Neurological Institute (patient information).
Mason AE, Hartogensis W, Chowdhary A, et al. A Randomized Trial Testing a Novel Mind and Body Intervention for Depression: CBT and WBH. Glob Adv Integr Med Health 2025;14:27536130251387714. NCT05708976.
Feasibility and acceptability of a Whole-Body hyperthermia (WBH) protocol. Int J Hyperthermia 2021. doi:10.1080/02656736.2021.1991010.
Evaluation of the Efficacy of Mild Water-filtered Infrared-A Whole-body Hyperthermia in Patients With Post-COVID Syndrome (HyPoCo). ClinicalTrials.gov NCT06204458.
FIR preclinical references (rat ischemic stroke; Alzheimer's mouse models): see companion TBI and Alzheimer's reviews.
