User blog comment:Miskos3/Fairy Tail Chapter 508: Pleasure and Pain, Review/@comment-27547436-20161031171812/@comment-7418318-20161031174625

I think the key is Mavis. Mavis had a very sorrowful life with barely any pleasure in it. She started out as something close to a slave, then had everyone she knew slaughtered, lived all alone for years and just when she finally go some friends, she was plunged into war and finally discovered that she's a ticking time-bomb that could kill her dear friends at any given moment.

But she did fall in love and kissed her lover... once. :'(

On the other hand Erza, who also fell in love with Jellal, only ever had this one possible kiss, that may or may not have been one in the manga and definitely wasn't one in the anime.

All the other people who were unaffected are also unlikely to have ever kissed a person they love romantically. Lucy never had a bodyfriend, Wendy and Romeo are too young for that kind of stuff (in context to the story, real life is a different matter), Erza is the special case mentioned above and Kagura might well have missed out on falling in love in her teenage days due to her vendetta against Jellal and just didn't meet "the one" in the year since overcoming that. And Warren... well... he isn't the most handsome man in Fairy Tail and he's not that old, so it's not impossible for him to never have fallen in love or be too shy toward women act on it... that and a potential tendency for being a lolicon, which would cut down on his chances further.

And August... well, he might have been a lonely hermit before Zeref picked him up, or just powerful enough to shrug off the magic, even though it would usually have affected him.