Low Level Laser Therapy for Hair Loss: Two Leading Hair Restoration Surgeons Explain What It Is and Why It Works
A conversation with Dr. Sara Wasserbauer and Dr. Robert Leonard, ISHRS members and hair restoration specialists.
Most people searching for answers about hair loss have heard of Rogaine. Many have heard of Propecia. But a surprising number have never heard of the third FDA-cleared treatment for hair loss – one that has been used clinically for more than three decades, has no known side effects, and works on a biological level that most patients never expect.
It’s called LLLT, low-level laser therapy for hair loss, also known as photobiomodulation or red light therapy. In a wide-ranging discussion, two of the field’s most experienced hair restoration surgeons, Dr. Bob Leonard and Dr. Sara Wasserbauer, sat down to talk through what it is, how it works, and why more patients should know about it.
What Is LLLT for Hair Loss — and Why Does It Have So Many Names?
If you’ve heard of red light therapy for hair loss, photobiomodulation, or cold laser therapy, you’ve already encountered LLLT – you just may not have known it by that name.
“Those three terms can be used interchangeably,” says Dr. Leonard. “Photobiomodulation is the medical term. Red light therapy is the popular consumer term. LLLT, or low-level laser therapy, is what most physicians in the field have called it for decades.”
The word itself tells the story:
- Photo = light energy
- Bio = biological tissue (in this case, your hair follicles)
- Modulation = producing a positive effect on those follicles using that energy
The therapy traces its origins to the 1960s, when Hungarian physician Dr. Endre Mester – now known as the “Father of Photobiomodulation” – made an unexpected discovery. While conducting cancer research on mice, a staff error accidentally set the laser to the wrong (lower) power level. Instead of the result he expected, he found something remarkable: hair was regrowing on the shaved backs of the mice.
“He admitted at a conference with his sons that one of the staff had the light turned on the wrong level,” Dr. Wasserbauer recalls. “It was supposed to be high, and it ended up discovering that lower-level light was growing hair. It was serendipity.”
That accidental discovery launched more than 50 years of clinical use and research, and today LLLT (also referred to as photobiomodulation or low-level light therapy) is one of only three treatments the FDA has cleared for hair loss, alongside minoxidil and finasteride.
How Does LLLT Actually Grow Hair?
Understanding why photobiomodulation works for hair loss requires a brief look at what happens to follicles as hair loss progresses.
Dr. Leonard uses what both doctors affectionately call the “birthday cake” illustration to explain it to patients. Healthy, thick terminal hairs are deeply rooted in the scalp, each one surrounded and nourished by a network of tiny capillaries – blood vessels that deliver oxygen and nutrients directly to the follicle. As androgenetic alopecia (genetic hair loss) progresses, blood flow to those capillaries gradually diminishes. The follicles become miniaturized. Hairs grow shorter, finer, and less pigmented until they eventually stop growing altogether.
LLLT intervenes at the level of those tiny capillaries.
“It works right in the tiny capillaries nourishing each of the follicles,” Dr. Leonard explains. “Not the coronary arteries – the capillaries. The hair is literally wrapped in these tiny little blood vessels, and laser therapy increases the flow to each one of them.”
But blood flow is only part of the picture. Dr. Wasserbauer describes several simultaneous mechanisms:
- Increased blood supply to the follicle – More oxygen and nutrients reaching the root.
- Upregulation of ATP production – ATP (adenosine triphosphate) is the energy currency of cells. When the light stimulates the cytochrome C oxidase photoreceptor in the follicle’s mitochondria, it essentially turns up the cell’s energy production, giving it more fuel to grow.
- Reduction of inflammation – Many patients with scalp conditions like psoriasis or lichen planopilaris report relief from irritation alongside their hair growth results. “After a couple of sessions, patients say their scalp doesn’t really burn anymore,” Dr. Wasserbauer notes. “It doesn’t feel like anything during treatment – it’s not a massage, it’s not warm – but you notice it’s doing something.”
- Upregulation of growth factors – Photobiomodulation appears to signal follicle cells to increase production of the biological growth factors that support hair cycling.
“On so many different levels, it’s going to be assisting with hair growth,” Dr. Wasserbauer says. “That’s the end result. It grows the hair.”
The Three FDA-Cleared Treatments – and Why More Is Better
One of the most important points both doctors make is about how photobiomodulation fits into a complete hair loss treatment plan.
There are exactly three treatments the FDA has cleared for hair loss: minoxidil (Rogaine), finasteride (Propecia), and laser/photobiomodulation therapy. Each one works on a different population of follicles through a different mechanism.”
Each of them has its own population of follicles upon which it works,” says Dr. Leonard. “But if you double up, it’s better than one. And if you triple up, it’s better than two.” Dr. Wasserbauer is more emphatic: “It’s not just additive. It’s actually multiplicative. So the more of these therapies one does, the better the efficacy.”
This is an important distinction for patients who assume that trying one treatment means they’ve exhausted their options. The three FDA-cleared approaches are designed to work together — and photobiomodulation in particular can be used safely alongside any other therapy, including surgery.
For a complete overview of red light therapy for hair loss — including the photobiology of hair growth, wavelengths, device types, and the science behind the biphasic dose response — visit the ISHRS guide: Red Light Therapy for Hair Loss
What the Data Says – and What 35 Years of Clinical Practice Shows
Dr. Leonard has been using photobiomodulation in his practice since 1990, making him one of the longest-practicing clinicians with this therapy in the world. The numbers he shares with patients come from direct observation across thousands of cases over three-and-a-half decades.
90% stabilization rate – In 90% of patients, photobiomodulation halts or significantly slows the progression of hair loss. For many patients, this is the primary goal: not necessarily growing new hair, but holding onto what they have.
60% regrowth – In 60% of patients, measurable regrowth of miniaturized hairs is observed.
Only 10% resume shedding after stopping – This figure is perhaps the most striking. When patients stop using minoxidil or finasteride, nearly 100% experience renewed shedding within months. With photobiomodulation, Dr. Leonard observes that only about 10% of patients who discontinue the therapy resume shedding. “That doesn’t happen with laser therapy,” he says. “And now with cap devices that people purchase and use at home, there’s really no reason to stop.”
Dr. Wasserbauer, who comes from a background in internal medicine and spent years skeptical of the therapy, puts the efficacy on par with minoxidil. “Some of the data is hard to compare because of how studies are designed,” she acknowledges. “But I tell patients it’s on the order of minoxidil – and when you add it to the other treatments, the benefit is multiplicative.”
The Post-Surgical Advantage
For patients who have undergone or are planning a hair transplant, photobiomodulation offers a set of benefits that both doctors consider significant.
Dr. Leonard’s early protocol involved offering office-based laser therapy twice weekly for two weeks beginning the day after surgery. His observations across those patients revealed three consistent outcomes:
Earlier regrowth. Transplanted hairs that fell out in the normal post-surgical shedding phase began regrowing at approximately eight weeks rather than the typical three to four months. “What we would see at nine months would be visible at maybe six months,” he notes.
Reduced shock loss. Post-operative shedding from existing hair in and around the transplant area, a common phenomenon known as shock loss, decreased dramatically in patients using laser therapy.
Faster overall results. The combination of earlier regrowth and reduced shedding meant patients saw results sooner, which matters enormously given that hair loss patients are “the most impatient patients in the world,” as Dr. Leonard puts it with a laugh.
“With transplants, with anything doing with the hair, people want everything done yesterday,” Dr. Wasserbauer agrees. “I think that’s why God put us in this field – to teach us patience.”
Compliance: The Real-World Factor
One of the most practical insights in the conversation concerns not the biology of the treatment, but the human factor of actually using it consistently.
Early cap devices were designed for 30-minute sessions every other day. Dr. Leonard found that compliance was a genuine problem – including for himself. “I’d go to dinner with my wife and come home at 11 o’clock at night and I’d had to have my cap treatment, and I went to bed. And if I remembered whether I did it yesterday or not, that was another issue.”
Working with manufacturers, he helped explore whether the protocol could be restructured. A non-pulsing laser device designed for six minutes daily, rather than 30 minutes every other day, showed equivalent efficacy in studies. But in clinical practice, Dr. Leonard observed something interesting: patients actually achieved better results with the newer protocol.
The reason? Compliance. “They were more compliant at six minutes every day versus a half hour every other day. And I saw better growth when they switched.”
“Use it faithfully,” Dr. Wasserbauer tells her patients. “Put it by your bed a couple of times a week, every two or three days. You pop it on, you get the light dose, and then it’s just that additive little bump.”
Is LLLT Safe?
Both doctors address safety concerns directly, because questions about light therapy and cancer risk, heat burns, and systemic effects come up constantly.
Cancer risk? Photobiomodulation uses non-ionizing radiation – light in the visible and near-infrared spectrum. It does not carry the energy required to damage DNA or cells. “It’s non-ionizing radiation,” Dr. Leonard explains, echoing the clarification made by Juanita Anders, a laser expert from the Department of Defense, at an international conference. “People just don’t understand what light does what.”
Burns? No. The devices do not generate enough heat to burn tissue. There is no sensation of warmth during treatment.
Pregnancy? Dr. Wasserbauer used photobiomodulation throughout her three pregnancies. “It’s local,” she emphasizes. “It’s going to just affect the stuff that it’s on. It’s not like finasteride being absorbed by the scalp and going systemic.”
Systemic effects? The localized nature of the treatment – light only affects the tissue it directly contacts – means there are no systemic concerns. The wound-healing research that preceded hair applications actually demonstrated this clearly: only the specific areas treated with light showed enhanced hair growth.
Who Benefits Most?
Both doctors discuss which patients are the best candidates, and which ones shouldn’t rely on photobiomodulation alone.
The therapy works by stimulating follicles that are miniaturized but still present. If follicles are completely gone, there is nothing left to stimulate.
The best candidates are patients in earlier stages of hair loss, which points to one of the most critical insights in the conversation. By the time a man or woman notices their hair is thinning, roughly 50% of their hair has already been lost.
“That horse is out of the barn long before you recognize something’s happening,” Dr. Leonard says. “And what we recommend as physicians who belong to and are leaders in the International Society of Hair Restoration Surgery: seek out medical therapies early. Go to a medical professional and find out what your options are.”
For women specifically, both doctors note that photobiomodulation occupies a uniquely important place in the treatment landscape. Finasteride is not typically prescribed for premenopausal women, leaving them with fewer options. “For our female patients who don’t have finasteride as a possibility,” Dr. Wasserbauer says, “this is one of the only things we have to treat them with that really works.”
Androgenetic alopecia – genetic pattern hair loss – affects one in two men and one in four women in the United States, totaling approximately 80 million people. For the vast majority of those patients, especially those who act before their hair loss is advanced, photobiomodulation is a meaningful part of the treatment picture.
A Practical Note for Travelers
In a lighter moment, both doctors agree on one highly specific piece of advice: always carry your laser cap in your carry-on luggage. “It is one of the number one most stolen things out of checked luggage,” Dr. Leonard warns. “Put it upside down in your carry-on bag with the battery inside and fill things around it.”
The Bottom Line from Two Physicians Who’ve Seen It Work
Dr. Leonard and Dr. Wasserbauer come to the same conclusion from different directions – Dr. Leonard from 35 years of clinical use and patient observation, and Dr. Wasserbauer from a background in evidence-based internal medicine who was, by her own admission, a skeptic before the clinical data and her own patient results changed her mind.
“Just don’t think of it as snake oil quite yet,” Dr. Wasserbauer says. “It has been around in clinical use since the 1960s, the evidence is building, and for patients who want to do everything they can for their hair — especially as an adjunctive therapy alongside surgery, minoxidil, or finasteride — it’s an easy thing to add in that really can be helpful.”
“I hope that whoever you go to will offer you photobiomodulation,” Dr. Leonard adds, “because it’s an excellent therapy to consider.”
Dr. Bob Leonard and Dr. Sara Wasserbauer are esteemed members of the International Society of Hair Restoration Surgery (ISHRS). To find a qualified hair restoration specialist near you, visit ishrs.org/find-a-doctor. For the complete scientific guide to photobiomodulation and red light therapy for hair loss, visit the ISHRS Red Light Therapy for Hair Loss resource page.