Aaron, you're going to have to do some deep cleaning once the cats are placed elsewhere. The dander. From:
What is cat dander - What causes dander and how does it afffect allergy victims
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.... 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.
*Fel d 1 is a protein that in cats is encoded by the CH1 (chain 1/Fel d 1-A) and CH2 (chain 2/Fel d 1-B) genes. Fel d 1, produced largely in cat saliva and sebaceous glands, is the primary allergen present on cats and kittens (
Fel d 1 - Wikipedia, the free encyclopedia).