Stability of PABA after UV irradiation in vivo and in vitro.

Sunscreens are widely used for the prevention of acute and chronic sun damage. One of the most widely used sunscreens is para-aminobenzoic acid (PABA). It has been reported that PABA decomposes on exposure to air and light as well as exposure to high doses of UVB. In the present study we found that PABA was stable during long-term storage. PABA seems to be stable after irradiation of physiological doses of UVA and UVB in vitro. However, the in vivo studies demonstrate that significantly less PABA could be extracted from UVA-irradiated sites compared to controls.