The excessive exposure to ultraviolet (UV) radiation is the main cause of skin cancer, the most commonly diagnosed cancer in the world. In this context, the development of innovative and more effective sunscreens, with bioactive compounds like caffeine, displaying antioxidant and anticancer potential, is required. This research work assessed
in vitro
and
in vivo
the efficacy and safety of topical sunscreen formulations containing caffeine as an adjuvant of the UV filters. Sunscreens were prepared with 2.5% w/w caffeine or in the absence of this compound. In order to evaluate the safety of these formulations,
stratum corneum
hydration, skin barrier and colorimetry were assessed
in vivo
in healthy subjects before and after skin treatment with the samples. The efficacy of the sunscreens was assessed
in vitro
, using PMMA plates and a spectrophotometer equipped with an integrating sphere; and
in vivo
by the determination of the sun protection factor (SPF). None of the formulations caused erythema or impaired the skin barrier function. The
in vitro
functional characterization showed higher SPF values for the caffeine formulation. The
in vivo
studies also confirmed the higher SPF value of the formulation combining caffeine with the filters, compared to the caffeine-free sample. This improvement contributed to an increase of, approximately, 25% in the
in vivo
anti-UVB protection. In conclusion, caffeine was well tolerated by the skin and increased the photoprotective activity, being a new alternative adjuvant in sunscreens formulation.
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