Low to moderate doses of infrared A irradiation impair extracellular matrix homeostasis of the skin and contribute to skin photodamage.

Human skin is daily exposed to sun rays, which include not only ultraviolet radiation, but also an important quantity of infrared (IR) radiation. In the past few years, many publications have underlined the negative impact of IR radiation on the human skin, particularly when the skin and/or the cells are exposed to high sun irradiance and significant doses of IR. In the present study, we demonstrate, in vitro on normal human fibroblasts, that even under low irradiance with single or very few repeated doses, infrared A irradiation (IRA) produces free radicals, triggers major changes in the expression of the type I collagen and elastin network, impairs the dermal-epidermal junction, upregulates several matrix metalloproteinases and has an impact on the expression of key genes of the extracellular matrix. We conclude that chronic or discretionary exposure to IRA could play a role that is more important than expected in premature skin aging.