Is photobiomodulation therapy free from racial bias?: a narrative review of skin pigmentation

BACKGROUND: Photobiomodulation therapy (PBMT) has been extensively researched for tissue repair, pain relief, and muscle recovery. However, melanin, a primary skin chromophore, can impede photon penetration into darker skin, potentially diminishing the efficacy of PBMT. Despite this, clinical protocols and guidelines seldom account for skin pigmentation when setting parameters, possibly exacerbating racial disparities in healthcare. OBJECTIVE: To examine the effect of melanin on the efficacy of PBMT and highlight the necessity for personalized strategies that account for skin pigmentation. DESIGN AND SETTING: Short communication conducted at the Universidade de São Paulo (USP), Ribeirão Preto, São Paulo. METHODS: A narrative review of PBMT mechanisms, light-tissue interactions, and the impact of melanin absorption on treatment outcomes was conducted. RESULTS: The clinical outcomes of PBMT depend on the technical parameters (wavelength, energy, and dose) and skin pigmentation. Darker skin tones with higher melanin content may lead to reduced photon penetration effectiveness. However, most studies and protocols do not consider this variable. Only a few clinical trials have categorized outcomes by skin tone, exposing a notable knowledge gap. CONCLUSION: Melanin plays a crucial role in PBMT response, and overlooking skin pigmentation in research and clinical practice could perpetuate disparities. Enhanced and tailored protocols are essential to optimize PBMT outcomes among diverse populations.