[quote=@YipeeXD]
A few pages back, the reason for just dragon slayers having motion sickness. 
I could warrant a pretty good guess why but I don't want to spoil fairy tail for anyone
[/quote]

Why? I've watched all the episodes and I can't figure it out.

Well except if I put science into it

 motion sickness is caused by mixed signals from your senses, i.e. your eyes tell you the train isnt moving as you are moving with it, however your sense of balance feels all the bumps and swaying and tells you that you are moving. The result is confusion leading to nausea.

 Dragon slayers are shown to have heightened senses, Natsu more so than the others. Probably because he is strong. So my guess is, stronger senses means stronger mixed signals and stronger motion sickness.


[hider=spoiler-open at your own risk]Also, sting or rouge (can't remember which) say that the motion sickness occurs when you become a real dragon slayer, in kther words when you reach a certain level of strength, which explains while Gajeel didn't originally have motion sickness. And Wendy either hasn't resched that yet, or her own healing magic prevents her from getting motion sickness[/hider]