It prevents the Propionibacterium acnes bacteria from replicating by preventing it from making vital proteins.
This leads to an accumulation of the skins natural oils and bacteria (Propionibacterium acnes) in the skin (which feed on the oils and keratin) which further inflame the gland causing acne.
The oxygen gas is absorbed into the pores of the skin, where it kills off the acne-causing bacteria Propionibacterium acnes.
The sulfacetamide inhibits the growth of the bacterium Propionibacterium acnes that is associated with acne, while sulfur facilitates the removal of dead skin cells to prevent clogged pores.