Recent studies have showed that infrared (IR) radiation is involved in photo-ageing of the skin. IR is the long wavelength part of the solar radiation that reaches the earth’s surface. It is subdivided into near IR (760-1,400nm) and far IR. Only near infrared, also called IRA, penetrates deep into the skin reaching the subcutis, whereas longer wavelength IR is absorbed in the epidermis, producing heat. UV radiation, which is of higher energy than IR radiation induces photochemical effects, such as DNA damage.
Furthermore, it is known that exposure of skin to UV induces the expression of matrix metalloproteinases (MMPs), enzymes responsible for collagen degradation and thus skin ageing. In 2008, Krutmann et al showed that IR radiation also induced an upregulation of the matrix metalloproteinase-1 (MMP-1) in human skin[1]. They found that IR radiation leads to the formation of