In Vitro Infrared (IRA-IRB)

Since Infrared (IR), including the IRA and IRB, is the most implicated in skin damage, IR protection factors should be comparable between products and provide the balance of UV, visible and IR protection within a single product. This innovative in vitro method consists in evaluating the IR protection levels expressed by the IR-CW (UV/VIS/IR balance) and the % IR (percentage of intensity of IR protection) from a sunscreen product through the full spectrum (from 290 nm to 2500 nm) measured by means of a spectrophotometric method. To take into account any potential photo-unstability, the product was pre-irradiated before measurement. Finally, this method relies on the use of in vivo SPF results for scaling the absorbance curve.