This page is written carefully, because people with this diagnosis have often been offered a great deal of confident nonsense, and because one feature of the condition makes some interventions actively harmful.
What the condition involves
Chronic fatigue syndrome, also called myalgic encephalomyelitis, is a serious condition characterised by profound fatigue and post-exertional malaise.
Post-exertional malaise is the defining feature and the one most often misunderstood. It is not ordinary tiredness after effort. It is a disproportionate worsening of symptoms, often delayed by a day or two, that can last days or weeks and can follow physical, cognitive or emotional exertion that would have been trivial before.
That single feature is why advice that works for ordinary fatigue can make this condition worse, and why graded exercise approaches have been substantially revised in clinical guidance.
Why light therapy was proposed
One of the leading research hypotheses involves impaired mitochondrial energy production, which is why photobiomodulation has been proposed as a candidate.
The logic is direct. If the problem is cells struggling to produce energy, and red and near-infrared light acts on the machinery of energy production, the two line up. It is a reasonable hypothesis rather than a marketing invention.
Reasonable hypotheses are still hypotheses.
What the evidence actually is
The direct evidence is very limited.
A small number of studies and case series report improvements in fatigue and pain scores, but they are mostly uncontrolled and too small to draw conclusions from.
Uncontrolled matters enormously here. Without a comparison group, you cannot distinguish treatment effect from natural fluctuation, and this condition fluctuates considerably. Someone starting a new treatment during a better patch will attribute the better patch to the treatment. That is not dishonesty, it is how uncontrolled observation fails.
Better evidence exists for fatigue in other contexts, notably multiple sclerosis and cancer-related fatigue, which is suggestive but not transferable.
Not transferable is the important phrase. Fatigue in MS, fatigue after chemotherapy and the fatigue of this condition are different phenomena with different mechanisms. Borrowing evidence across them is exactly the move that produces overclaiming.
The caution that matters most
Post-exertional malaise means that anything increasing activity or heat load needs caution.
Read that as written. It is not a generic disclaimer.
Light therapy sessions involve getting to the device, positioning, holding still, and heat. For someone within a narrow energy envelope, that is a real demand, and heat load is itself a trigger for many people with this condition. Many also experience orthostatic intolerance, meaning standing or sitting upright is harder than it sounds.
If you try this, treat it as you would any new activity: introduce it very gradually, at a fraction of the usual duration, and watch for delayed worsening over the following two or three days rather than judging by how you feel during the session.
If you decide to try it
- Start extremely short. Two or three minutes, not twenty
- Lying down if upright posture is difficult
- Keep the room cool and the panel further away than instructions suggest
- Wait several days between increases, because post-exertional malaise is delayed
- Change one thing at a time, so any change can be attributed
- Keep a record, including the days after, not just the day of
- Stop if you get delayed worsening. That is a clear signal, not a setback to push through
Speak to someone who knows your case
If you have this diagnosis, discuss any new intervention with a clinician who knows your case.
Pacing, meaning staying within your energy envelope rather than pushing through, is the approach most current guidance supports. Anything that risks pushing you over that limit deserves discussion first.
It is also worth periodically revisiting whether anything else is contributing. Thyroid disease, anaemia, B12 deficiency, sleep apnoea, coeliac disease and medication effects all cause fatigue, are testable, and are sometimes missed alongside an existing diagnosis.
Common questions
Does red light therapy help chronic fatigue syndrome? Direct evidence is very limited. A small number of studies and case series report improvements, but they are mostly uncontrolled and too small to draw conclusions from.
Why is it being investigated? One leading hypothesis involves impaired mitochondrial energy production, and light acts on mitochondria.
Does evidence from MS fatigue apply? No. It is suggestive but not transferable, because the underlying mechanisms differ.
Is it safe with post-exertional malaise? It needs caution. Anything increasing activity or heat load can trigger it, and the response is often delayed by a day or two.
How should I start? Very short sessions, cool room, and several days between any increase, watching for delayed worsening.
Where this leaves things
A plausible hypothesis with very little direct evidence behind it, and a condition where caution is not optional. We would rather set that out plainly than sell you certainty that does not exist.
If you decide to try it, do so slowly and with a clinician who knows you. Browse our Future Form systems, or read related pages on MS fatigue and sleep.
