Cutibacterium acnes is associated with the exacerbated inflammation of acne vulgaris, which occurs through the immune induction and pathogenicity factor production. Sebum, which is not present in the growth medium currently used to study acne, is present in acne pustules in differing concentrations among the pathological stages, such as the initial formation and inflammatory phase. To evaluate the effect of C. acnes on inflammation exacerbation in acne pustules in vitro, we developed an skin sebum medium containing artificial sebum and studied the growth and pathogenicity factor production of C. acnes in the skin sebum medium. The growth and lipase activity of C. acnes ATCC11828 were tested using skin sebum medium containing different sebum concentrations. Only lipase activity decreased in the skin sebum medium culture containing 0.5 % sebum when compared with that without sebum, while both growth and lipase activity decreased in cultures with 1.0 % sebum. Therefore, the growth and lipase activity of C. acnes changed in the presence of sebum. Furthermore, when the growth and lipase activity of C. acnes were tested in skin sebum medium containing sebum components, unsaturated fatty acids, such as oleic acid and triolein, led to a decrease in lipase activity without inducing a change in growth. In the presence of oleic acid, C. acnes lipase activity decreased noncompetitively in a concentration-dependent manner. Our data showed that C. acnes growth and lipase activity changed upon sebum addition to the skin sebum medium, and acne inflammation caused by C. acnes needs to be studied under conditions similar to those in acne pustules.