[Coony]

It doesn't mean when you don't see the dirt in your cat & it is clean. I have heard of cases whereby a cat owner become allergic to the cat after a few years & in most of this cases it is due to the cleanliness of their cats, like not bathing the cat for a long long time even though it doesn't look dirty at all. There are thing that are far worst then dirt that you can see with your eye, for instant like germ, bacteria & cat dander that can cause allergy.

Cat dander consists of microscopic pieces of dry cat skin which becomes airborne, landing on bedding, curtains, carpeting, and other surfaces, including humans' skin and clothing. Cat dander particles are tiny, about 1/10th the size of dust mites. Dry skin particles wouldn't be particularly allergenic except for this factor: Fel D1(Fel d-1, Fel d 1)

Fel D1 may come from the Latin Felis Domestica. It is a glycoprotein found in the cat's sebaceous glands under the skin, to a lesser degree in cats' saliva, and in cats' urine. When a cat grooms his coat, the Fel D1 present in his saliva lands on the cats' skin and hairs, and combined with the Fel D1 from the sebaceous glands, creates a sort of "double whammy" to allergy sufferers.

Interestingly, the production of Fel D1 appears to be more or less prolific in different types of cats:
Whole cats produce more Fel D1 than neutered cats
Male cats, particularly unaltered, produce more allergens than female cats.