Wound healing remains a critical challenge in clinical practice, with difficult-to-heal lesions posing significant burdens on patients’ quality of life and healthcare systems worldwide. Traditional therapeutic approaches, ranging from pharmacological interventions to physical therapies like ultrasound and electrotherapy, often have limitations in achieving consistent and satisfactory outcomes. In recent decades, low-power light therapy has emerged as a promising alternative, sparking growing interest in the clinical potential of light-emitting devices such as LASER (Light Amplification by Stimulated Emission of Radiation) and LED (Light Emitting Diode). However, debates have long surrounded the therapeutic equivalence of these two light sources, with questions about whether their biological effects and optimal parameters align.
To address these critical gaps, a comprehensive review published in Anais Brasileiros de Dermatologia (https://pmc.ncbi.nlm.nih.gov/articles/PMC4148276/) systematically analyzed 68 in vitro and animal studies conducted between 1992 and 2012. The research, led by Maria Emília de Abreu Chaves and colleagues from renowned Brazilian institutions including the Universidade Federal de Minas Gerais (UFMG) and Pontifícia Universidade Católica de Minas Gerais (PUC Minas), aimed to clarify two core objectives: identifying the biological effects that support LED use in wound healing and defining its optimal parameters, while comparing these with those of LASER.
Key Findings: Biological Effects—LASER and LED Are More Alike Than Different
A central revelation from the review is that LASER and LED induce remarkably similar biological responses that promote wound healing. Both light sources were found to reduce inflammatory cell infiltration, enhance fibroblast proliferation, stimulate angiogenesis (the formation of new blood vessels), accelerate granulation tissue formation, and boost collagen synthesis—all essential processes for effective tissue repair. These effects were consistently observed across in vitro models (e.g., cultured fibroblasts) and animal studies (rats, mice, rabbits), confirming that the therapeutic potential of low-power light is not exclusive to LASER’s coherent light properties, as some previously hypothesized.
Notably, the review dispelled the myth that coherence (a unique characteristic of LASER, where light waves travel in a single direction with uniform frequency and phase) is a prerequisite for therapeutic efficacy. LED, which emits non-coherent light, demonstrated comparable biological activity to LASER, suggesting that the cellular response to photostimulation depends on light parameters rather than coherence. As highlighted in the study, coherence is lost when light interacts with biological tissues, rendering it irrelevant to the photobiomodulation process.
Optimal Parameters: Wavelength and Dose Take Center Stage
The review also underscored that the biological effects of both LASER and LED are highly dependent on irradiation parameters, with wavelength and dose being the most critical.
For LASER, the most commonly used wavelengths ranged from 632.8 to 830 nm (red to near-infrared), while doses predominantly fell between 1 and 5 J/cm². Doses exceeding 10 J/cm² were found to exert inhibitory effects on cell function, aligning with the Arndt-Schultz curve—a principle stating that low doses of a stimulus produce beneficial effects, moderate doses are optimal, and high doses are inhibitory. For example, a dose of 4 J/cm² was shown to be more effective than 8 J/cm², while doses of 10 and 16 J/cm² hindered healing processes.
LED shared similar parameter ranges: wavelengths predominantly spanned 627 to 670 nm (red spectrum), with a predominant optimal dose of 4 J/cm². Doses for LED ranged from 0.1 to 10 J/cm², and like LASER, doses within the 1–5 J/cm² range yielded the most significant therapeutic benefits. The consistency in parameters between the two light sources further supports their interchangeability in wound healing applications.
Additionally, the review identified an “optical therapeutic window” in the red and near-infrared spectral ranges (600–1000 nm). Light in this range achieves maximum tissue penetration, as shorter wavelengths (blue and green) are strongly absorbed by chromophores like hemoglobin and melanin. While some studies using blue or green light still observed biological effects, red and near-infrared light remain the preferred choice for clinical applications due to their superior tissue penetration.
Implications for Clinical Practice
The findings of this review have profound implications for clinical practice. By demonstrating that LED and LASER offer comparable therapeutic effects with similar optimal parameters, the research validates LED as a cost-effective, accessible alternative to LASER for wound healing. LED devices are typically more affordable, portable, and easier to operate than LASER systems, making them particularly valuable in resource-limited settings or primary care environments.
However, the review also emphasized the need for standardized treatment protocols. The variability in wavelengths, doses, and study methodologies across the analyzed literature highlights the importance of defining consistent parameters to ensure reproducible outcomes. Future clinical studies—especially human trials focusing on LED—are warranted to translate the in vitro and animal findings into evidence-based clinical guidelines.
Conclusion
Low-power light therapy, whether delivered via LASER or LED, represents a safe and effective therapeutic modality for promoting skin wound healing. Their shared biological effects and optimal parameters challenge the historical preference for LASER and position LED as a viable, patient-centric option. As research continues to refine treatment protocols, low-power light therapy is poised to become an indispensable tool in the management of acute and chronic wounds, improving patient outcomes and reducing healthcare burdens.
To delve deeper into the comprehensive analysis of studies, biological mechanisms, and parameter details, access the full review here: Effects of low-power light therapy on wound healing: LASER x LED