Red light for pain. Red light for skin. Red light for energy, which is the one aimed at you, because somebody has worked out that exhaustion is a reliable market.

So here is the whole picture, including the part where it works, which is narrower and more interesting than either side will tell you.

Start with the mechanism, since this is not magic beans. Red and near infrared light reaches a little way into skin. The leading explanation is that an enzyme in your mitochondria absorbs it, which nudges energy production. Plausible, but incomplete. Researchers still argue the details, which is not the same as no idea.

The evidence splits by what you ask it to do.

The strongest case is in cancer care. Guidelines recommend light therapy to prevent painful mouth ulceration in particular groups, such as people having radiotherapy for head and neck cancer. That came from trials with hard endpoints.

There is reasonable support for wound healing, some muscle and joint pain, and hair growth in pattern hair loss. Skin studies show small improvements in fine lines. Those are the wins, and notice how specific they are.

And now the part sold to you. There is no good evidence that it treats fatigue, lifts energy or improves immunity, and none supporting it as a general treatment for a long term condition. Where it has been tested and helped, the claim stayed narrow. The mitochondria talk does the work in the broad version, and nobody checks what the trials found. Mostly small, early and inconclusive.

Two things decide whether a device can do anything. First, wavelength. Useful ranges are roughly 600 to 660 nanometres for red, around 800 for near infrared. Second, dose: the light falling on an area of skin multiplied by how long you sit there. More is not better: the curve often rises and then falls, so a long session can do less than a short one.

Here the home market gets difficult. Many panels and masks deliver a fraction of the output used in studies, and most listings never publish the numbers. You are sold a trial run on another machine.

The honest summary: a narrow proven range inside a huge marketing operation, and none of it is what you were hoping for.

So the question before you buy anything:

Today’s Practice

A buying filter, not a practice. Five minutes with the listing.

On a hard day, buy nothing and let the advert go. The boundaries: do not stare into the lights, use any eye protection supplied, since near infrared is invisible and brightness is no guide. Stop if skin blisters or burns. If you have a light-sensitive condition such as lupus, ask your doctor first. If your fatigue is new or worse, that is a doctor, not a purchase. No lamp replaces an investigation.

What the Research Says

The mouth ulceration evidence deserves a closer look, because it shows what good evidence in this field looks like. The trials randomised people, used an outcome you can see and grade rather than a questionnaire, and ran where the alternative was considerable pain. Several professional bodies reviewed that body of work and recommended light therapy for specific groups receiving specific treatments. Compare the energy claims, which rest on small studies, varied protocols, soft outcomes and industry funding. It is the same technology. The difference is entirely in what was asked of it and how carefully anyone looked.

From the Old World

Light as medicine has a longer history than the current marketing suggests. In 1903 a Danish physician, Niels Finsen, received a Nobel Prize for treating a disfiguring tuberculosis of the skin with concentrated light, mostly ultraviolet, a different part of the spectrum from the masks. Alpine sanatoria built whole balconies for sun treatment. Some of it worked, particularly before antibiotics, and some was applied far beyond what it could do. That is the pattern worth carrying. Light does something, the something is specific, and enthusiasm has run ahead of it once before.

Come Home

Five lines, before you open the shopping app.

One act for today, if you want one. Find one red light product online and look for the wavelength and the power per area. Notice whether they are there.

The technology does something specific. What is being pointed at your exhaustion is not that.

P.S. Tomorrow, the season, and why your appetite has changed without asking your permission. Root vegetables, and what the old systems made of the shift.