It isn't the length of the hair that people are "allergic" to...it's
the dander and stuff that comes off the animal that you can't see.
Nonetheless, feeding your cat quality food can actually help minimize
shedding and improve the coat and skin.

Although I am certainly not a doctor, I would say that much of the
"I'm allergic to cats" is just hype.  Once you have one in your home
that you live with, your body and immune system will adjust to the
animal over time.  This is usually what happens when someone moves,
for example, to another part of the country and their body experiences
different natural allergens.

Hope this helps.