Low-level laser (light) therapy (LLLT) in skin: stimulating, healing, restoring

Abstract

Low-level laser (light) therapy (LLLT) is a fast-growing technology used to treat a multitude of conditions that require stimulation of healing, relief of pain and inflammation, and restoration of function. Although skin is naturally exposed to light more than any other organ, it still responds well to red and near-infrared wavelengths. The photons are absorbed by mitochondrial chromophores in skin cells. Consequently, electron transport, adenosine triphosphate nitric oxide release, blood flow, reactive oxygen species increase, and diverse signaling pathways are activated. Stem cells can be activated, allowing increased tissue repair and healing. In dermatology, LLLT has beneficial effects on wrinkles, acne scars, hypertrophic scars, and healing of burns. LLLT can reduce UV damage both as a treatment and as a prophylactic measure. In pigmentary disorders such as vitiligo, LLLT can increase pigmentation by stimulating melanocyte proliferation and reduce depigmentation by inhibiting autoimmunity. Inflammatory diseases such as psoriasis and acne can also be managed. The noninvasive nature and almost complete absence of side effects encourage further testing in dermatology.

Figure 1

Mechanism of action of LLLT. Basic biological mechanism behind the effects of LLLT is thought to be through absorption of red and NIR light by mitochondrial chromophores, in particular cytochrome c oxidase (CCO) which is contained in the respiratory chain located within the mitochondria ^–. It is hypothesized that this absorption of light energy may cause photodissociation of inhibitory nitric oxide from CCO leading to enhancement of enzyme activity , electron transport , mitochondrial respiration and ATP production ^–. In turn, LLLT by altering the cellular redox state can induce the activation of numerous intracellular signaling pathways; alter the affinity of transcription factors concerned with cell proliferation, survival, tissue repair and regeneration^,,,,.

Figure 2

Tissue penetration depths of various wavelengths.

Figure 3

Examples of LLLT devices in dermatology for home and clinical use.

Figure 4

Possible mechanism of actions for LLLT’s effects on skin rejuvenation. LLLT aids skin rejuvenation through increasing collagen production and decreasing collagen degradation. Increase in collagen production occurs by LLLT’s increasing effects on PDGF and fibroblast production which happens through decreasing apoptosis, increasing vascular perfusion, bFGF and TGF-β. Decrease in IL-6, and increase in TIMPs which in turn reduce MMPs all aid in reduction of collagen degradation.

Figure 5

Illustration of acne treatment with red and blue light. Red and blue light when used in combination have synergistic effects in treatment of acne. P. acnes synthesizes and stores a large amount of porphyrins. Once the porphyrin is exposed to visible light (specifically blue light) it becomes chemically active and transfers to an excited state, resulting in formation of reactive free radicals and singlet oxygen which in turn causes membrane damage in P. acnes ^,. Red light is proposed to exert its effects through reducing the inflammatory process ^,.