Light-Based Treatments and Devices

PHOTOBIOMODULATION (LOW LEVEL LASER LIGHT THERAPY) 38309304, 38307144​​

Introduction

Definition(s)

• PBM is a light therapy using red (620–700 nm) and near-infrared (700–1440 nm) light delivered through low-level lasers or LEDs.

• Watts = joules/second

• Joules = unit of energy

• Fluence = joules/area

Mechanism of Action

• Light interacts with photoacceptors in the skin (mainly COX in mitochondria) - this is contrast to lasers which target chromophores (melanin, heme, opsin)

• Biological effects include changes in ATP, reactive oxygen species, nitric oxide levels, and calcium.

• Modifies gene expression, cellular proliferation, and inflammatory pathways.

Penetration Depths

• 633 nm RL: 1-3 mm

• 810 nm NIR: 2-10 mm

• 1072 nm NIR: 5-10 mm

Conditions Treated and Treatment Notes

Cancer Therapy Side Effects (Radiation dermatitis, mucositis, lymphedema)

• Wavelength: 808–905 nm or red light (620–670 nm).

• Treatment Course: 1–12 minutes/session immediately after radiation therapy; total duration varies based on condition (e.g., daily treatments for several weeks).

• Effects: Reduces inflammation, erythema, pain severity, and lymphedema.

Alopecia (Androgenic alopecia, alopecia areata)

• Wavelength: 630–800 nm.

• Treatment Course: 10–25 minutes/session, 2–3 times per week for 16–24 weeks.

• Effects: Stimulates hair growth, increases density, and prolongs the anagen phase - proposed mechanism is by stimulating release of paracrine growth factors from dermal papilla cells. 

• Studies:​​

Meta-analysis of photobiomodulation for the treatment of androgenetic alopecia. J Dermatolog Treat. 2021. PMID: 31746251.

• Looked at various laser diode and LED devices both in comb and hat delivery mechanisms for treatment of androgenic alopecia.

• Overall, there was a statistically significant effect. 

  • Laser diodes appeared better than LED/laser diode combos, though all showed efficacy over placebo/sham/non-treatment areas.

  • Comb was not statistically better than hat devices, but was numerically better.

• I pulled a couple specific studies (30569416, 28489273) representing studies with best and worst results.  The challenge in visual interpretation is the hair styles and lengths between pre and post treatment were often different making it hard to tell what the real visual impact of the intervention was.  

  • Suchonwanit et al 2018 (30569416) used a 224 laser diode helmet with 660nm wavelength, max optical power 5mW capable of delivering a fluence of 3.5mW/cm2.  Exposure for 19min resulted in a 4 J/cm2 total energy delivery. This study showed the most significant results in the meta-analysis, but the example photographs were challenging to interpret as it appeared the hair length was not the same in each photograph.          ​

  • Esmat et al 2017 (28489273) used a 21 laser diode, 30 LED helmet with 655nm wavelength, <5mW output for 25min.  They did not specify the fluence that was delivered to the scalp so total energy delivered is not available for comparison.  This study had the lowest standardized mean difference between treatment and control groups, but the highest overall response and the photographs selected as examples were more impressive, but again the hair styles appeared different making direct comparison challenging.  

Photobiomodulation Therapy With Different Wavebands for Hair Loss: A Systematic Review and Meta-Analysis. Dermatol Surg. 2022. PMID: 35510860.

• Systematic review and meta-analysis that showed that ultraviolet light was effective in treating AA, red light was effective in treating AGA, and infrared light was effective in treating both AA and AGA.

Clinical Safety and Efficacy of Dual Wavelength Low-Level Light Therapy in Androgenetic Alopecia: A Double-Blind Randomized Controlled Study. Dermatol Surg. 2025. PMID: 39679573.​

• This double-blind randomized controlled trial evaluated the efficacy of three LED caps (REVIAN LED “smart cap”) emitting red (625/660 nm), blue (425 nm), or both wavelengths versus a sham device in treating androgenetic alopecia. After 16 weeks of daily 10-minute treatments, the pooled active treatment groups showed a statistically significant net increase of 28.5 hairs/cm² compared to sham (p = 0.033), with blue light (Cap 102) yielding the highest numeric hair count gain and red light (Cap 101) achieving the best cosmetic appearance by physician assessment. However, by week 26, hair gains were not maintained, likely due to poor compliance, and individual cap comparisons were underpowered due to high exclusion rates.

Ulcers (Diabetic ulcers, chronic wounds)

• Wavelength: 630–980 nm.

• Treatment Course: 2–20 minutes/session, 2–7 times per week for at least 4 weeks.

• Effects: Accelerates wound healing, decreases inflammation, and reduces pain.

Herpes Simplex Virus (HSV)

• Wavelength: 670–1072 nm.

• Treatment Course: 2–5 minutes/session, 2–3 times per week during outbreaks.

• Effects: Speeds up lesion healing, reduces symptoms, and prevents recurrences.

Acne Vulgaris

• Wavelength: 620–750 nm.

• Treatment Course: 10 minutes/session, 3–5 times per week for a minimum of 4 weeks.

• Effects: Reduces lesion count, inflammation, and sebum levels.

Skin Rejuvenation (Improvement of elasticity, hydration, and photodamage)

• Wavelength: 620–1072 nm.

• Treatment Course: 10–20 minutes/session, biweekly to daily for 4–16 weeks.

• Effects: Enhances collagen production, reduces wrinkles, and improves skin tightness.

Wounds and Scars

• Wavelength: 630–830 nm.

• Treatment Course: 1–10 minutes/session, 3–4 times per week for a minimum of 1 week.

• Effects: Promotes healing phases, reduces scar thickness, and improves pliability.

PBM in Skin of Color

• Patients with darker skin may experience increased sensitivity to visible light, resulting in post-inflammatory hyperpigmentation.

• Recommendations:

  • Start with conservative dosing and increase parameters gradually.

  • Begin at 50% of manufacturers’ recommended settings and monitor for adverse effects​​​