If I've been doing something where I know I'm sweaty and would not be smelling pleasantly (anything that makes me sweaty like working out) I would shower first. However, if I've had a normal day it isn't necessary.
Usually, my guy doesn't want/need me to, but if it is after a long day and I've been sweating, whether he asks me to or not, I am at the least going to clean up if not completely shower before he goes down on me.
I always try and use an Eden wipe or something prior to him going down on me, though.
If you're JUST going down on her, nothing else? No shower necessary, unless you're so dirty that you smell. If the oral sex is going to transition to other sexual activities (especially her going down on you), then yeah, a shower would be nice.
I've never been too concerned about it. It only 'bit' me once when I tried to go down on a girl for the first time - I almost threw up. I've never had a problem with my wife - she's more worried about it that me.
Do you think a shower is necessary before going down on a female partner, not necessary or optional?
I personally don't take a shower specifically for that purpose, but I never skip a shower. I don't shower before my partner does that for me because I don't need to. I don't have downstairs issues. No odors, problems or anything like that. Thankfully! No period to worry about so I'm good in that dept. He is happy that way and insists on doing it before intercourse. Lucky me