Alahmadi M. et al. - Photobiomodulation and Androgenetic Alopecia: A Systematic Review and Meta-Analysis

Low-level laser therapy, which falls under the category of photobiomodulation, is associated with an increase in capillary density and hair shaft thickness in androgenetic alopecia. This review also covered fractional lasers, which are not a form of photobiomodulation and whose results are not included here.

What this study measured

Androgenetic alopecia is a progressive form of hair loss that responds only to a limited extent to medication. This systematic review with meta-analysis, conducted in accordance with PRISMA guidelines, evaluated energy-based devices for this condition, drawing on 37 studies and a total of 3,298 patients. This total encompasses two very different categories: on the one hand, low-level laser therapy (LLLT), a form of photobiomodulation that does not alter the skin; on the other hand, fractional lasers, including ablative CO₂ lasers, which create controlled micro-lesions on the scalp and do not fall under the category of photobiomodulation. This page includes only the figures attributable to low-level laser therapy. The abstract does not specify how many of the 37 studies focused on LLLT, nor does it provide a PROSPERO number.

Key Findings

Here are the combined data for low-level laser therapy, either alone or in combination with minoxidil.

• Hair density: an average increase of 18.56 hairs per square centimeter compared to the placebo
• Hair shaft thickness: an average increase of 10.62 micrometers compared to the placebo
• Low-level laser therapy combined with minoxidil: an additional gain of 11.75 hairs per square centimeter compared to minoxidil alone
• Tolerability: adverse effects described as mild and transient; this observation applies to all devices studied

No confidence intervals are provided for these estimates, which makes it impossible to assess their accuracy.

How photobiomodulation works for this indication

The mechanism remains hypothetical. Red and near-infrared light is thought to be absorbed by cytochrome c oxidase in the hair follicle’s mitochondria, which would increase the production of ATP available to a highly active hair matrix. This signal could prolong the hair’s growth phase, known as the anagen phase, delay the transition to the resting phase, and modulate local oxidative stress as well as peri-follicular microinflammation. Improved microcirculation is also suggested. None of these mechanisms are measured here.

Limits You Should Know

The most significant limitation stems from the structure of this review: it combines, within a single analysis, low-level laser therapy—which is a form of photobiomodulation—with ablative and non-ablative fractional lasers, which act through controlled thermal damage and are not a form of photobiomodulation. The authors’ general conclusion—which favors fractional lasers combined with minoxidil, PRP, or growth factors—cannot be applied to photobiomodulation and is not repeated here. There are additional caveats: no confidence intervals, no GRADE assessment, an unspecified number of studies on LLLT, and an unspecified follow-up period. Since androgenetic alopecia is chronic, the question of whether the results are sustainable remains open.

What This Means in Practice

These figures position low-level laser therapy as a supplementary option, with a measurable but modest effect when compared to normal scalp hair density. Combining it with minoxidil yields better results than minoxidil alone, which supports its use as a supplement rather than a replacement. The abstract does not specify the wavelength, power, or frequency of sessions. A dermatological evaluation remains useful to rule out other causes of hair loss.

Frequently Asked Questions

Does low-level laser therapy really promote hair regrowth?

In this review, it was associated with an average increase of 18.56 hairs per square centimeter compared to a placebo, and with hair shafts that were 10.62 micrometers thicker. This is an improvement in density measured in studies, not a complete restoration of hair, and results vary from person to person.

Should photobiomodulation be combined with minoxidil?

The data support this: combining low-level laser therapy with minoxidil results in an additional gain of 11.75 hairs per square centimeter compared to minoxidil alone. This combination requires a medical decision, as minoxidil is a medication with its own precautions for use.

Fractional laser and photobiomodulation—are they the same thing?

No. Photobiomodulation, or low-level laser therapy, uses low-intensity light that neither heats nor damages the skin. Fractional lasers, including ablative CO₂ lasers, intentionally create micro-lesions and are considered medical procedures performed in a clinic. The results of one cannot be applied to the other.

Reference

Alahmadi M, et al. Lasers and Energy-Based Devices in the Treatment of Androgenetic Alopecia: A Systematic Review and Meta-Analysis. Skin Appendage Disorders, 2026. PMID 42339398. View the study on PubMed

This summary is provided for informational purposes only and does not constitute medical advice. Photobiomodulation is not a substitute for prescribed treatment. Consult a healthcare professional.