We report the in vitro inhibition of Propionibacterium acnes (P. acnes) by a bacteriocin-like inhibitory substance (BLIS-like substance) produced by Streptococcus salivarius (S. salivarius). Bacteriocins are proteinaceous substances produced by bacteria that are capable of inhibiting the growth of similar bacterial strains. Unlike classical antibiotics, they have a relatively narrow spectrum of killing activity, resulting in a reduction in the intensity of selection for resistance. These findings suggest that BLIS may potentially be used for its anti-P. acnes activity in the treatment of acne.