This first. I used to be allergic, but mostly grew out of it. If it's been a while since he was around a cat, try going to a shelter and just see how he reacts. You may be surprised. Also, it may only be long haired cats, or even specific breeds. A friend just got a kitten and we visited. The kitty plopped herself on my lap most of the time we were there. I coughed and my eyes watered. It was half Siamese (or is it Thai-ese now? 😁). Their other cats never bothered me.
Now onto the story. Having eight cats myself, I thought it was great. I went through what Maison did, although I wasn't cat sitting. Our Calico went missing, when she was really young. I looked all over, walked around outside; nothing. A little while later I was wondering why a couple of the other cats were so interested in the dishwasher. Yep, she had crawled behind it. She still hides, but I don't worry about it so much. I've found pretty much all of her hiding spaces. Looking forward to more chapters after Secret Author is done.