ELI5: Why is it that a mouthwash is not effective to prevent *bacterial* STI infection acquired through oral sex, given that a standard mouthwash can kill 99.9% bacteria?

r/

Just to clarify, I’m after knowing the aspect of prevention such as having mouthwash before oral sex, thus before potential exposure to bacteria-causing STIs (e.g., gonorrhoea, chlamydia). My question is NOT about viral infections.

Comments

  1. AL4-Chronic Avatar

    Because you’re not washing you’re mouth out while you’re performing the act so you’re ingesting even just trace amounts of bodily fluids during the act

  2. TampaFan04 Avatar

    because math? .1%. Multiply that by a few hundred million… Thats… millions of bacteria entering your mouth.

    Sorry about your mouth STDs, must suck.

  3. I_Guess_Naught Avatar

    One major concern is cuts/abrasions in your mouth (which are so common you should just operate under the assumption you always have them) which would let you get infected almost instantly with at least some small number of pathogens regardless of what mouthwash you use.

    If mouthwash is used after sex, it could help clear some bacteria away after the fact but the exposure through cuts or for the duration since the oral sex would remain.

    If mouthwash is used before sex, the trace amounts staying in your mouth would have minimal effect- if it were strong enough to protect against anything and everything with just the residue your partner receiving oral would be complaining of burning before much else happens.

    My uninformed assumption on the 12 hr protection you mentioned is that it’s the time from when the mouthwash is used until the bacterial population in your mouth recovers enough to do anything we consider relevant (odor, tooth decay). It’s not the period in which your mouth is actively a bacteria killing room.