What it is
Hydroxycinnamic acid belongs to the family of phenolic acids found widely in plants, related to compounds such as ferulic, caffeic, and coumaric acids. In skin care and sun care formulas it is included chiefly for its antioxidant properties, helping to limit oxidation within the product and on the skin. It is a supporting ingredient rather than a UV filter.
Safety & warnings
Phenolic acids of this type are generally well tolerated at the low levels used in cosmetics. As with many plant phenolics, very sensitive individuals could occasionally experience irritation, but it is not a recognized common allergen.
Origin & sourcing
Occurs naturally in many plants as part of the phenylpropanoid pathway; the cosmetic ingredient may be plant-derived or produced synthetically.
Questions everyone asks
What does hydroxycinnamic acid do in sunscreen?
It acts mainly as an antioxidant, helping protect the formula and skin from oxidative stress; it is not itself a UV filter.
Is it related to ferulic acid?
Yes. Ferulic, caffeic, and coumaric acids are all hydroxycinnamic acid derivatives within the same phenolic-acid family.