What Causes Dry Patch On Lip Followed By Swelling?

Hi... I infrequently get a weird dry patch on my upper lip - it even has a different texture to it. Just like a slightly rough dry patch, but it doesn t hurt, tingle or peel - just feels dry, textural and tight. This is often followed by (or proceeded by) my entire upper lip becoming swollen to the point of it being hard to smile. Oh and it looks as if I ve just gotten lip injections - It makes a great free botox joke! There is no food related rhyme or reason, no environmental rhyme or reason - and more often than not I just consider it a stress illness. Lately though, it just never seems to fully go away, so I m asking...