serum in Polish

Blood serum used as a blood product, in the practice of medicine: blood serum from the tissues of immunized animals (human or nonhuman), containing antibodies and used to transfer immunity to another individual (human or nonhuman).

(skincare) A skincare product of varying consistencies with a high concentration of one or more active ingredients, for a targeted purpose, such as preventing acne, repairing sun damage, or moisturizing.