Ask the internet whether red light therapy really works and you will get two confident answers, one enthusiastic and one dismissive, both of them louder than the evidence. The honest answer is quieter than either, and it's far more useful once you have it.
Does red light therapy work for hair loss? The short answer
Yes, for the right hair, by a modest amount, over months. That sentence has three qualifications in it, and the qualifications are where all the useful information lives.
Low-level red and near-infrared light has been studied for pattern hair loss for years, in men and in women, and the trials point the same general way. On heads where the follicles are still alive and producing finer hair than they used to, regular treatment tends to produce measurable gains: more hairs growing in a given patch of scalp, and each of those hairs a little thicker.
Measurable is the word worth holding on to. These are gains you find by counting hairs in a marked square of scalp, which is a different thing from gains that announce themselves across a room. The reason they show up at all is that the light is working on follicles that are still working, and the mechanism itself has a piece of its own: what red light therapy actually does to a follicle.
Low-level laser therapy, LLLT, red light therapy: one treatment, four names
Part of what makes this question hard to settle from a search bar is that one treatment answers to four different names. You will find it as low-level laser therapy, usually shortened to LLLT, as red light therapy, as photobiomodulation, and on our own price list under its clinical name, photodiode therapy.
That matters because it makes the field look more contradictory than it is. Studies differ in the device, in how much light it delivers and in how long people kept using it, and those differences produce different results, which is not the same as a disagreement about whether light does anything at all.
What "modest" honestly means for you
A trial reports what happened on average across a group of people, and an average is a real number that belongs to nobody in particular. It carries the same sort of information as the average rainfall for a month where you live: enough to tell you to take a coat, and no use whatsoever for predicting Tuesday.
So inside any good result there are people who did noticeably better than the average and people who saw nothing they would have spotted themselves, and there is no way to know in advance which of those you'll be. That isn't a flaw in the treatment. It is what an honest average looks like when you hold it up against one person.
What it does not do
It does not put hair on a bald, shiny scalp. An area that went smooth years ago has no working follicle left in it, and light only ever encourages something that is already growing, which is the whole reason this treatment belongs to thinning rather than to baldness.
It is not a substitute for surgery either. Where an area has emptied completely and the back and sides are still strong, the only thing that puts hair back there is a transplant, and our hair page sets that day out in full. Whether the operation would be worth it for you is a separate question with its own answer.
And it is not a single event. Trials that find something find it after months of regular treatment rather than after one sitting, which is exactly why the light comes here as a course of six sessions, £500 for the six, rather than as a single appointment.
Why it is slow, and why the photographs are so unreliable
Think of the oil in a car engine. Nobody has ever watched the level drop, because it goes down across thousands of miles, and the only reason anybody knows about it is the dipstick: a thin steel stick with two marks near the end. Those marks mean something only because the check is done the same way every time, with the car standing level, the engine off and settled, and the stick wiped clean and pushed the whole way home before it comes back out to be read. Take the reading on a slope five minutes after a fast run, and the stick will show you a litre missing that never went anywhere.
Photographs are the stick, and this is why before and after pictures of light therapy are among the least trustworthy on the internet. What the light does over a few months is small enough that the ordinary accidents of taking a picture can each be bigger than the treatment underneath them, so two honest photographs taken carelessly can invent an improvement or bury a real one. Matching a pair is the whole of the skill, and how to read a pair of hair photographs sets out what has to be held still, all of which works just as well on pictures of your own head.
Who it genuinely suits
The pattern that suits it best is early thinning, in either sex: nothing missing from anywhere, everything simply finer than it used to be. Thinning spread across the whole head sits in the same place, which is why light comes up so often in treatment for women, where that pattern is the common one.
It also works comfortably beside PRP, which is £250 a session and comes at the same follicles from a different direction.
Then there is the case people rarely think of. Transplanted follicles hold on to their resistance to the hormone behind pattern loss wherever they are put, which is why the result lasts. The hair standing between them never had that resistance, and goes on thinning exactly as it would have done anyway. Looking after that hair is a sensible thing to do after surgery, and it is one of the ordinary reasons people have light treatment.
Clinic lamp, or a cap at home
It's the question that follows almost immediately, and it has the least satisfying answer, because what decides the outcome isn't where the light comes from. It's how much light actually reaches the scalp, and how regularly it gets there.
It's rather like learning an instrument. Twenty minutes on most days will take you somewhere; three hours once a month will not; and the make of the piano is a long way down the list of things that decide which of those you get. Light works on the same terms. What counts is the dose the device delivers, repeated on a schedule you will actually keep, for long enough to cross the months that hair growth needs.
A clinic course puts a known dose under the clinic's lamp on a schedule somebody else keeps for you. A device at home puts a daily habit in your own hands, for as long as you keep it up. Both are answering the same two questions, dose and repetition, and those are the two worth asking of anything you are thinking of buying.
How you would know it was working
Take one photograph a month, matched to the last one, and then leave the stack alone for a while. Three to six months is the honest interval before judging anything you do for thinning hair, because a follicle works to a calendar of months rather than weeks, and nothing on the surface can move faster than the cycle underneath it.
What you're looking for at the end of that is not hair standing in places that had none. It is how much scalp shows through the parting, and whether the ends have more to them than they did in the first picture you took.
Finding out whether your own hair has something to work with
Everything above turns on one thing: whether the follicles in the area that bothers you are alive and underperforming, or finished. That is a question about your scalp rather than about the treatment, and it isn't one to settle from photographs on the internet.
It is exactly what the free consultation is for. Around thirty minutes, on video, any evening from 6pm, with the team that would treat you at our CQC-registered Leeds clinic. They'll look at your pattern and your donor density, tell you honestly which path fits, and say so plainly if the answer is that you don't need anything yet.
Book the free consultation and have somebody look at your scalp properly before you spend anything on it.