CalleighDoodle why the ffs?! Just because i said it was messing around? I didn't comment on whether it was immature or not, I said it was messing around, which it is!!!!
Look op, yes, in light of everything else it could be suspicious, however poking a tongue out at someone you're clearly friends with is hardly a hanging offense is it?
Like I said previously, if I was friends and ONLY friends with someone at work and i became the subject of malicious rumours then NO, I wouldn't change the way I acted around them because I would have done nothing wrong in the first place, and I'd hope that my husband would trust me enough for this not to matter. On the other hand, you could argue there's no smoke without fire.
As a pp said though, you can't have it both ways, so say he stops being friendly with her at all, stops any sort of contact except where necessary for his job, would that make you any less concerned? Wouldn't you then think well they were clearly right as he has stopped the friendship. He can't win here, and sadly it seems nor can you at present.
In order to get past this you need to stop analysing everything, him poking his tongue out is clearly friendly, but hardly the sign of a raging affair is it. I'd let that bit go. It all boils down to whether you trust his word I'm afraid. I hope you can find a way through this, but try not to let it consume you.