What are the adverse effects of low-level laser therapy (LLLT) or photobiomodulation (PBM) on the scalp?

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Last updated: April 1, 2025View editorial policy

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From the Guidelines

Red light therapy on the scalp is generally considered safe with minimal side effects, primarily including temporary redness, mild headaches, and eye strain if proper precautions are not taken. When considering the application of red light therapy, particularly on sensitive areas such as the scalp, it's crucial to weigh the potential benefits against possible adverse effects. The evidence from dermatological guidelines, such as those provided by the British Association of Dermologists and British Photodermatology Group 1, although focused on photodynamic therapy (PDT), highlights the importance of understanding and managing potential side effects related to light therapy on the skin.

Some key considerations for the safe application of red light therapy on the scalp include:

  • Limiting exposure to recommended durations to avoid overheating or excessive light exposure.
  • Maintaining an appropriate distance between the device and the scalp to prevent burns or intense heat.
  • Using protective eyewear during treatment sessions to prevent eye strain or damage.
  • Starting with fewer sessions per week and gradually increasing frequency as tolerated by the individual.

While the provided study 1 discusses the adverse effects of topical photodynamic therapy, such as pain, particularly in areas like the head and neck, it's essential to note that red light therapy, when used correctly, operates at different parameters (e.g., wavelength, intensity) that are designed to be safer and less invasive. However, individual reactions can vary, and monitoring for any signs of discomfort or adverse effects is crucial. Rare reports of increased hair shedding initially after starting red light therapy have been noted, but this typically resolves as the body adjusts to the treatment.

Given the current understanding and the focus on minimizing morbidity, mortality, and improving quality of life, the use of red light therapy on the scalp, when applied judiciously and with proper precautions, can be a relatively safe adjunctive treatment for various scalp and hair conditions. It's always recommended to consult with a healthcare professional before starting any new therapy to discuss potential benefits and risks in the context of individual health needs.

From the Research

Side Effects of Red Light Therapy on the Scalp

  • The studies 2, 3 found no adverse events or side effects reported for red light therapy on the scalp for treating androgenic alopecia in both males and females.
  • Another study 4 mentions that low-level light/laser therapy (LLLT) with near infrared (NIR) and visible red light has strong penetration and encouraging photobiomodulation for treating psoriasis, but does not specifically mention side effects on the scalp.
  • A comparative study 5 between blue and red light for treating psoriasis found clinical improvement with both, but no major differences in side effects were reported.
  • A review of clinical applications of low-level light therapy 6 states that it is a safe and effective method for skin rejuvenation, treatment of acne vulgaris and alopecia, but notes that methodologic flaws and industry funding may impact the quality of evidence.

References

Guideline

Guideline Directed Topic Overview

Dr.Oracle Medical Advisory Board & Editors, 2025

Research

A clinical review of phototherapy for psoriasis.

Lasers in medical science, 2018

Research

Efficacy of blue light vs. red light in the treatment of psoriasis: a double-blind, randomized comparative study.

Journal of the European Academy of Dermatology and Venereology : JEADV, 2012

Professional Medical Disclaimer

This information is intended for healthcare professionals. Any medical decision-making should rely on clinical judgment and independently verified information. The content provided herein does not replace professional discretion and should be considered supplementary to established clinical guidelines. Healthcare providers should verify all information against primary literature and current practice standards before application in patient care. Dr.Oracle assumes no liability for clinical decisions based on this content.

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