Androgenetic alopecia (AGA), the most prevalent type of hair loss, affects over half of men and women. While only two drugs, minoxidil and finasteride, have been approved for its treatment, and hair transplant remains another option, low-level laser therapy (LLLT) has emerged as a new, safe, device-based modality for stimulating hair growth in both sexes.
Hair loss can significantly impact an individual's confidence and quality of life. The pursuit of effective hair restoration methods has led to the development of various innovative treatments, including laser hair restoration. This article explores the effectiveness of LLLT in treating hair loss, examining its mechanisms, clinical evidence, and practical applications.
AGA, also known as male or female pattern baldness, is a common condition influenced by genetics and androgens like testosterone and dihydrotestosterone (DHT). In men, hair loss typically manifests as a receding hairline and thinning at the crown, while women experience a more diffuse thinning across the scalp. AGA affects 50% of males over the age of 40 and 75% of females over 65.
In 1951, William James Hamilton described his system for grading male-pattern baldness. The Hamilton classifications are as follows:
The most commonly used classification system to quantify hair loss in women was presented by Dr. Erich Ludwig in 1977. His proposed classification system consists of three grades of hair loss:
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With most patients responding to anti-androgen treatment, scientists assume that female pattern baldness is an androgen-dependent condition.
The most common treatments for AGA include topical minoxidil, finasteride (for males only), and surgical hair transplantation. However, these options may not be effective for all patients, require indefinite use, and can be limited by side effects, cost, or donor hair availability.
Low-level laser therapy (LLLT) involves exposing biological tissues to coherent, collimated, monochromatic light to induce therapeutic benefits. It utilizes low-intensity light, typically in the red to near-infrared spectrum (600-950 nm), to stimulate cellular activity. The overall effect of LLLT on the body is known as photobiomodulation.
In 1967, Mester et al. discovered the ability of lasers to induce hair growth using low-intensity light while treating cancer in mice. This accidental finding paved the way for exploring LLLT as a hair loss treatment.
LLLT is thought to stimulate anagen phase re-entry in telogen hair follicles, prolong the duration of the anagen phase, and increase proliferation rates in active anagen hair follicles. The speculated mechanism involves direct stimulation of hair follicle stem cells in the bulge region, inducing differentiation and proliferation via increased heat shock protein (HSP) levels, such as HSP27.
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The most widely accepted mechanism is that LLLT displaces nitric oxide from COX allowing an influx of oxygen to bond to COX and progress forward in the respiratory process to ATP production and ROS signaling. These effects further lead to increased cellular proliferation, modulation in levels of cytokines, growth factors, and inflammatory mediators, and increased tissue oxygenation.
LLLT exhibits a biphasic dose response, meaning that small doses stimulate, moderate doses inhibit, and large doses kill. The effects of LLLT depend on irradiance (power density) and illumination time rather than fluence (energy density).
Numerous studies have investigated the efficacy of LLLT in treating AGA. These studies have shown that LLLT stimulates hair growth in both men and women.
A systematic review and meta-analysis investigated the effectiveness of FDA-approved LLLT devices for pattern hair loss (PHL) treatment. The meta-analysis comprised seven double-blinded, randomized, controlled trials. The overall quantitative analysis yielded a significant increase in hair density in those treated by LLLT versus sham groups. The subgroup analysis demonstrated the increased hair growth in male and female subjects with both comb- and helmet-type devices.
Initially, lasers were used as hood. But the penetration to scalp was questionable, especially in females with long hair. Later in 2007, Laser HairMax® comb was approved by the FDA for LLLT in hair loss for AGA, initially for men. In 2011, it was approved by the FDA for female pattern hair loss also. Another home therapy device called laser cap was also approved by the FDA. It has an advantage of full scalp coverage and even distribution. Recently, non-laser devices such as light-emitting diode (LED) have also been tried. The most commonly used devices have wavelengths in the range of 650-1200 nm and fluences of 1-10 J/cm2, with a power density of 3-90 mW/cm2.
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NASA played a role in creating Light-Emitting Diodes (LEDs), which are now used in many biomodulating treatments. In 1998, Professor Harry Whelan and his group at the NASA Space Medicine Laboratory developed a phototherapy source that was more effective than previous laser treatment.
Various LLLT devices are available, including laser combs, helmets, and caps. These devices deliver low-level laser light to the scalp, stimulating hair follicles and promoting hair growth.
The HairMax Lasercomb® was the first LLLT device approved by the FDA for treating AGA. Clinical trials have demonstrated its effectiveness in increasing hair count, density, and thickness.
The iGrow-II Hair Growth System consists of 21 red visible light LDs and 30 red LEDs configured within an outer helmet and protective inner liner. The use of LDs and nonlaser LEDs provides a full coverage of the upper one-third of the head (i.e., the area commonly covered with stylized hair). The helmet system automatically pauses the therapy if the subject’s head moves outside of the zone of radiation. The therapy will resume when the correct head position is re-established.
The Capillus272 Pro consists of 272 red, visible light of 650nm LDs. Each LD emits a power of 5mW, with a density of 2.34mW/cm2. The device is configured within an outer helmet and protective inner liner for portable use, a rechargeable battery, and an adapter, and it can automatically pause therapy.
LLLT offers several advantages as a hair loss treatment:
Despite its potential benefits, LLLT has some limitations:
During laser hair removal, a laser emits a light that is absorbed by the pigment (melanin) in the hair. The light energy is converted to heat, which damages the tube-shaped sacs within the skin (hair follicles) that produce hairs. Although laser hair removal effectively delays hair growth for long periods, it usually doesn't result in permanent hair removal. Multiple laser hair removal treatments are needed for initial hair removal, and maintenance treatments might be needed as well.
As phototherapy treatment becomes more widely accepted, the many applications increase, including:
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