Many people find wringing a (water) wet wash clothe out tightly
and rubbing it all over the cat daily accomplishes as
much as "Allerpet". Takes all of three minutes, and that way,
the cat isn't dealing with something it's probably not going
to like the smell, or taste, of...

Before we start picking on kitty, beyond a rubby-dub with
a barely damp wash clothe, how's the rest of the house?
Running hepa filters (air purifiers)?
Pleated filters for furnace and ac?
Hepa vacuum?
Old carpeting? Old furniture? (get rid of it)  
Existing carpets kept shampooed frequently?
Well actually, you aren't supposed to have carpeting,
beyond washable rugs.
Drapes and stored clothes washed frequently?
Treat the surface of existing furniture.
Truly allergic? Not even supposed to have upholstered furniture.
Vinyl covers on box springs and mattresses?

No being lazy and slathering master with yucky (to him)
stuff, till you've gotten the rest of your house/problem
in order!

"What about treating the animal?
Allerpet-C was tested with two other suggested "treatments" for pets:
weekly distilled water baths, and daily doses of the tranquilizer,
acepromazine. The 1995 study found that none of these treatments
reduced the shedding of allergen."