BACKGROUND: Today, the sun protection factor (SPF) value of sunscreen products 
is determined in vivo with a standardized protocol (EN ISO 24444:2010), and the 
measured SPF biological end point is the visible skin erythema. However, many of 
the sunscreen products currently available on the market have antiphlogistic 
ingredients, which may potentially result in an overestimated SPF of the 
sunscreen.
AIMS: To investigate the potential influence of the antiphlogistic ingredients 
panthenol and bisabolol in sunscreens on the determined SPF value in vivo.
METHODS: Formulations with different concentrations of the antiphlogistic 
ingredients bisabolol or panthenol were tested. As a reference, a base 
formulation (vehicle) without antiphlogistic ingredients was used. First, the 
SPF of the sunscreen formulas with and without antiphlogistic ingredients was 
analyzed in vitro. To investigate whether the antiphlogistic ingredient may 
suppress the inflammatory response to ultraviolet (UV) irradiation, the SPF was 
determined in vivo. Finally, selected formulations were also analyzed in an 
erythema model for testing formulations on UV-induced inflammation.
RESULTS: It could be confirmed that no differences between the formula with and 
that without the active antiphlogistic ingredients bisabolol or panthenol exist 
when measured in vitro. However, there was also no statistically significant 
difference in the erythemal response between the vehicle (without an 
antiphlogistic active ingredient) and the test formulations with different 
concentrations of the antiphlogistic active ingredients in the in vivo 
determination of the SPF. Evidence of anti-inflammatory activity of the 
sunscreen antiphlogistics bisabolol and panthenol was also not apparent in the 
UV model over a time course of 48 h. Conlusion: The antiphlogistic ingredients 
panthenol and bisabolol incorporated in the tested sunscreen formula do not 
interfere with erythema reddening and thus do not affect the SPF value in vivo.