The present invention provides methods, products, and compositions for selectively inhibiting the growth of Staphylococcus aureus without preventing the growth of Lactobacillus species. Specifically, the present invention discloses the use of tetrahydroiso alpha acid or hexahydro beta acid at a concentration effective to inhibit the growth of S. aureus without preventing the growth of Lactobacillus. The inhibition of S. aureus in accordance with the present invention thus provides useful methods, compositions and products such as feminine hygiene products for treating the diseases associated with S. aureus infections and infestations, i.e., toxic shock syndrome, without disrupting the normal bacterial flora in the area of its application.