There are a number of mechanisms. First, just wiping off excess oil using a clean paper towel can help prevent acne. So the face wipes can help even if they had no other ingredients at all.
Face wipes also include detergents that make the oils wash away easily. Some use alcohol to both remove oil and kill germs.
But the three main acne fighting ingredients are salicylic acid, benzoyl peroxide, and benzalkonium chloride.
We discussed benzalkonium chloride when we talked about Bactine™ earlier. It kills germs by breaking up their cell walls and disabling their enzymes.
Salicylic acid works by penetrating the hair follicles (the cells in the pore that create hair) and removing dead cells that can clog the pores. It causes the dead cells to swell up with water, helping to push them out. It is thus useful for preventing acne in the first place, and less useful for treating pimples that are already inflamed.
Benzoyl peroxide kills the primary type of acne forming bacteria, Propionibacterium acnes. It is thus the opposite of salicylic acid, in that it is good for inflamed pimples, and doesn’t do much for blackheads and whiteheads. Benzoyl peroxide kills germs by breaking down and releasing free oxygen, which burns the bacterial proteins. Bacteria cannot develop resistance to this type of anti-bacterial agent.
Benzoyl peroxide may also act as an irritant, causing the cells in the pores to grow faster and slough off faster, pushing out the waxy sebum that plugs up the pore. Because benzoyl peroxide dissolves in fats, it can penetrate into the sebum and get into the pore, where water based medicines cannot.