Infrared- a Source of Free Radicals that is not Blocked by Sunscreens.
Up until recently, UV was considered to be the most damaging radiation of the solar spectrum for our skin while infrared (IR) was thought to be benign due to its relatively low energy.
However, recent studies have shown that IT, especially near IR, induces a significant production of free radicals in the dermis and diminishes the skin´s antioxidant capacity*.
Besides, sunscreens used in sun products neither filter nor reflect IR radiation and do not prevent the formation of IR-induced free radicals **.
This is especially an issue when-despite using sun protection products-we expose our skin for several hours to intense sunlight (i.e. when at the beach). Indeed this type of protection blocks the appearance of the sunburn, which is a signal that the skin has started to experience damage. Sun products with a high SPF allow us to prolong our sun exposure by preventing a part of the damage induced by UVB and UVA, however, they also permit the accumulation of damage induced by the other radiations such as IR.
Near Infrared (IRA) Penetrates Deep into the Skin
The sun radiation that reaches the skin is constituted by only 7% of UV, 39% of visible light and 54% of IR**. IR is invisible to the human eye but we can feel it as heat. Compared to UV, IR is characterized by long wavelenghts of low energy.
IR is divided into the following three categories: IRA (from 760 nm to 1400 nm), also called near infrared, represents the fraction that is the closest to the red visible light, IRB and IRC (from 1440 nm to 1 mm). Unlike IRB and IRC, IRA penetrates deep into the skin (two-thirds reach the dermis) and does not significantly increase the skin temperature.
*Schroeder et al., Infrared A Radiation Effects on the Skin. Piel, 2011, 26(6), 259-62
**Dupont et al., Beyond UV radiation: A skin under challenge.
Int J Cosmet Sci, 2013, 35, 224-32
Source: Mibelle Biochemistry