Photodamaged skin displays distinct clinical and histological features affecting the epidermis and dermis. Clinical features of photoaging include rhytids, skin textural irregularities, dyschromia and lentigines, and dilated capillaries. Histological features of photoaging include actinic dyskeratosis and thinning of the epidermis, dermal collagen degradation, and increased numbers of abnormal elastic fibers.

These changes in dermal and epidermal integrity associated with photoaging are thought to result from four main mechanisms: (1) the altered proliferative capacity of keratinocytes and fibroblasts, (2) the decreased biosynthetic capacities of fibroblasts, (3) the impaired intrinsic repair mechanisms of skin-derived cells, and (4) the increased production of metalloproteinases and other degrading enzymes.

Traditional ablative modalities used for photorejuvenation, including CO2 laser, erbium laser, and chemical peels, result in skin repair via direct tissue ablation and wound healing. Although very effective, these therapeutic modalities are associated with significant downtime and potentially serious complications, including skin infections, scarring, and permanent dyspigmentation. These limitations have motivated researchers to look for noninvasive alternatives that would modulate skin biology and promote tissue repair without injury. LED technologies fall under this category of photomodulating devices.

Different wavelengths have been studied and found to have beneficial photomodulating effects at the cellular level. Red light (633 nm) irradiation has been shown to increase fibroblastic activity and collagen production in vitro. Red light was also shown to increase fibroblastic growth factor production by macrophages and to diminish activity and viability of mast cells.