Oh and after is too late - once you are infected, you are infected. Washing, using dettol or purell (US product), etc., isn't going to change a thing.
Aj
NO.
Dettol will NOT be able to clean all the bacteria - it can't get INSIDE where many stds live, and in fact, could irritate your skin if you use it before sex, thereby making it EASIER to get an std or HIV.
There isn't a lot of risk with oral - a possible risk, but its not huge - but absolutely in no way should you consider unprotected anal sex EVER safe unless you are with a long term monogamous partner who has tested negative for any and all stds.
Aj