Sniffles, I think you got that name regarding the allergies eh?
First off, if your friend don't mind, make sure the cats can be brushed. You might or might not know this, but it's not the hair that we are allergic to, it's the cat's saliva. They clean themselves with the saliva and then it gets on the hair. So it's not just the cat/s, it's anything the cat licks or gets the hair after it cleans itself on. Brushing the cat before and after visits will help.