Low-level laser therapy for androgenetic alopecia
I Background
Low-level laser therapy (LLLT) has been employed in the clinical management of androgenetic alopecia (AGA) for over a decade. Due to its proven efficacy and high safety profile, it is now included in the AGA treatment guidelines of Europe, Japan, and China. Various models of LLLT devices have received certification from the National Medical Products Administration (NMPA) and are extensively used in clinical practice. This consensus, based on recent domestic and international guidelines and clinical research, aims to provide a reference for the correct selection and application of LLLT in clinical settings. The consensus has been registered with the "International Practice Guideli
nes Registry and Transparency Platform," registration number: PREPARE-2024CN277.
Low-level laser is a type of low-power or low-energy radiation laser that generates minimal heat, hence it is also known as "cold laser" or "soft laser." When applied to cells, low-level laser produces biological effects, a regulatory action on biological organisms termed "photobiomodulation." Currently, the commonly used wavelength range for low-level laser in the treatment of AGA is 650-670nm.
Androgenetic alopecia (AGA) is the most common type of hair loss, characterized by the progressive miniaturization of hair follicles beginning during or after puberty. It is associated with genetic, androgenic, and metabolic factors, presenting as a receding frontal hairline and/or progressive thinning and hair loss at the crown. Both men and women can be affected, but it is more prevalent in men, with incidence increasing with age. Current treatment options for AGA are limited. Common pharmacological treatments include oral finasteride (1 mg/day) and/or topical minoxidil (2% or 5%). Oral finasteride is approved only for male patients; minoxidil requires daily application and may cause local irritation, allergies, or hypertrichosis in non-alopecic areas, making long-term adherence challenging. Multiple clinical studies have shown that after 24 weeks of LLLT treatment, hair loss in AGA patients is controlled with minimal adverse effects, making LLLT a viable adjunctive physical therapy for AGA.
II Mechanism of Action
The mechanism of action for LLLT in treating hair loss remains unclear. Some studies suggest that the primary target is cytochrome C oxidase in mitochondria. LLLT may promote the release of nitric oxide (NO) from cytochrome C oxidase, alleviating NO's inhibitory effect on cellular respiration, activating the electron transport chain, and increasing ATP production. Additionally, the released NO can dilate blood vessels, enhancing oxygen utilization by tissue cells. LLLT also modulates transcription factors, such as nuclear factor KB (NF-KB) and hypoxia-inducible factor-1 (HIF-1), triggering downstream biological effects that promote the proliferation and migration of cultured cells in vitro.
III Treatment options for Patients
LLLT can serve as an adjunctive therapy for patients with AGA. For mild AGA cases, it can be used alone or in combination with pharmacological treatments. For moderate to severe AGA cases, it is recommended to combine LLLT with medication or other comprehensive treatment approaches.
For AGA patients who decline pharmacotherapy or experience adverse reactions to medication, LLLT can serve as a therapeutic option.
AGA patients undergoing hair transplantation surgery may also opt for LLLT as an adjunctive therapy during the perioperative period.
IV Common device parameters
Currently, the commonly approved wavelength range for medical and home-use LLLT devices by the NMPA is 650-670 nm, with a maximum power of ≤5 mW per laser head. Clinicians should provide personalized guidance to patients in selecting LLLT devices suitable for their use.
V Treatment Regimens
5.1 Current Common Treatment Regimens in China
There are currently various models of LLLT devices available. It is recommended to select the frequency and duration of treatment based on the respective device's instruction manual. For most LLLT devices, the treatment regimen typically involves daily or alternate-day irradiation, with each session lasting 20-30 minutes, for a continuous duration of over 3 months.
5.2 LLLT as a Monotherapy for AGA
Systematic reviews of AGA treatment have indicated that LLLT can effectively promote hair growth in AGA patients. In two multicenter, randomized, double-blind, controlled studies, involving 110 male patients and 225 (103 male, 122 female) AGA patients respectively, treatment with low-level laser comb and sham device over a 26-week follow-up period demonstrated a significant increase in hair density in the LLLT group. A retrospective study including 878 AGA patients treated with LLLT for 6 months showed effective rates of 51.9% and 57.4% for mild and moderate to severe AGA patients, respectively. In a double-blind, randomized sham-controlled study, 36 AGA patients treated with LLLT for 24 weeks showed significantly superior hair density and diameter compared to the control group. Another retrospective study involving 38 AGA patients treated with LLLT for 6 months showed a gradual increase in treatment efficacy from the first month to the third month and up to the sixth month, with efficacy rates of 52.9%, 64.5%, and 79.3%, respectively. At the end of the treatment course, the efficacy rates for mild, moderate, and severe AGA patients were 77.8%, 76.9%, and 42.9%, respectively. None of the mentioned studies reported any severe adverse reactions during the treatment process.
5.3 LLLT Combined with Pharmacotherapy for AGA
Three randomized controlled studies have compared the efficacy of LLLT combined with oral finasteride (1 mg/day) versus LLLT alone or finasteride alone in treating male AGA patients. The first study included 39 patients and showed that after 6 months of treatment, both the LLLT monotherapy group and the combined therapy group experienced significant increases in hair density, with the combined therapy group achieving better results; additionally, 62% of patients reported a noticeable reduction in scalp oiliness. The second study involved 208 AGA patients and demonstrated that the combined therapy group had significantly higher hair density compared to the finasteride-alone group. The third study, involving 448 AGA patients, found that the combined treatment was more effective than finasteride alone, particularly in patients under the age of 40.
LLLT Combined with Topical Minoxidil for AGA
There are also reports on the combined use of LLLT and topical minoxidil for treating AGA. In a randomized controlled study involving 90 AGA patients, it was found that the combination of LLLT and 5% topical minoxidil significantly improved both hair diameter and hair density compared to LLLT alone and minoxidil alone. The combined treatment group also showed a significant reduction in sebum secretion compared to the minoxidil-alone group, suggesting that the combined use of LLLT and 5% minoxidil can markedly enhance therapeutic efficacy.
VI Adverse Reactions and Their Management
LLLT has a low incidence of adverse reactions, which are generally mild, indicating a good safety profile. Common adverse effects include headaches, skin pain and burning sensation, itching, erythema, acne, and mild paresthesia. Occasionally, patients may experience tinnitus, ear pain, numbness in the forehead, and temporary telogen effluvium, but these symptoms are mild and typically resolve without treatment.
VII Patient Education
Patients should be clearly informed that AGA requires long-term and consistent treatment. LLLT is a safe and effective adjunctive therapy for AGA and can also help control sebum secretion. Typically, at least three months of consistent use is necessary to evaluate its effectiveness. The combination of LLLT with other pharmacological or non-pharmacological treatments yields better results. Given the varying parameters of different LLLT devices, patients should carefully read the user manual before use to understand the correct usage methods and precautions to ensure both efficacy and safety. When using large LLLT devices, protective eyewear should be worn; when using home LLLT devices, direct exposure of the laser beam to the eyes should be avoided. Although LLLT has a good safety profile, it is not recommended for use by pregnant women.
VIII Limitations
While the efficacy and safety of LLLT have been widely acknowledged, the evidence supporting LLLT for treating AGA is currently limited to a small number of randomized controlled trials or cohort studies. Moreover, most clinical studies have relatively short follow-up periods, lacking long-term follow-up data. Therefore, further research is needed to provide additional evidence and support for the use of LLLT in AGA treatment.
IX Conclusion
LLLT has been demonstrated to promote hair growth and, in clinical practice, it has gained widespread recognition among both patients and physicians due to its convenience, efficacy, and safety. Therefore, it can be considered as one of the treatment options for AGA patients as an adjunctive therapy.