I'll have another try. I was a bit tired last night, and today reading my post I sound a little flippant. I did not mean to be, for as you all are well aware, this is a serious issue for us all.
Let me expand a bit on what I tried to say last night (above).
I'll start with BB, as he replied to me.
The raw egg thing was a bit too light hearted I think. But what I was trying to say was that Listerine is an oral hygiene agent, designed to help with the bacteria that cause teeth and mouth problems such as calculus and bleeding gums. Help, not be 100% effective killer (you still need to brush, floss and toothpick - although if you're like me the last can play hell with bleeding gums). It is not designed to have an effect on viral infections, which of course are the ones we shake rattle & roll about when we're considering or dealing with dollops of delicious cum in our gobs. So: no real effect of any kind there other than placebo (THINKING you're doing good, so makes you feel better) Hence my flippancy about raw egg.
Second and more generally: chlamydia is one of the most common STIs. I believe I read somewhere it is THE most common in the USA. If left untreated it can cause complications, but rarely in males (and that includes LBs, as we're talking genetics here). Essentially for men you get the results I mentioned above: pain, swelling, rashes, etc. It is easily and effectively treated with antibiotics. Advice: get regular checkups.
Same goes for all the other ones you can get treatment for: gonno, syphyllus, all the various herpes, the two relevant heps (the third hep is not transferable in cum). Again: regular checkups for diagnosis and treatment. Although for some like at least one of the herpes, I believe there is still no cure.
Then there is HIV. We all know about that one, though new drugs to suppress (not cure, yet) are coming onto the market every year.
Now, behaviour. Take all precautions. Abstain if you must. Use condoms if you must.
But know this: in all reputable research with big samples thus far done - that I am aware of anyhow - the demonstrated risk of HIV transmission via oral sex is less than 1% or around that figure. In the most reputable research I've seen, it is 0.something %, so close to zero it doesn't matter. (And in fact in one European study with large sample, it was zero, ie not one person contracted anything.)
Summary: As long as you have healthy mouth and throat, your chances of getting HIV through sucking cock and drinking cum are very close to zero. Now, this is where Listerine comes in. It helps to keep your mouth healthy, along with brushing and flossing. But like I said above, it won't stop anything, it just helps you get the healthy mouth.
If like me you are addickted to oral sex you can pursue it with confidence that while you may get something, the chances of it happening with healthy gob are extremely slight for the main bads, and smallish (compared to vaginal or anal sex) for the others like chlamydia.
Declaration: I am not a medico and this is not guaranteed medical advice. But as a life long dedicated cock sucker I have keen interest and maintain a close watch on this stuff.