Is someone who has one (or more) Allergy/ies and is always bitching about it, so that they, and the people around them, can't enjoy their time at all.
It's a subdivision of attention whores.
"Oh I can't hug any of you because you all ate from that Nutcake and I'm allergic to nuts"
We couldn't enjoy the picnic because Laura was bitching
about her allergies all the time; She was acting like such an allergy whore.