So I went to a reputable pet store and bought Zodiac Spot On Flea Control for Cats and Kittens which promises to kill flea eggs in the animal's fur. You apply it just like the Revolution. So we did this on Saturday to all four of our cats.
By Sunday one of them was sporting a bald spot between his shoulder blades. Although we had noticed that it had aggravated them when we had put the medication on their shoulders for a little while after, we didn't make any connection between what was happening with him and the Spot On until we noticed his skin where the hair had fallen out looked like it had been burned it was so bright red and weepy.
His hair had fallen out in little clumps in that area, I found it lying in a cluster on the carpet. It wasn't like it had shed or anything because it wasn't loose hairs, you could see it formed into clumps with the roots and everything. He's a shorthaired cat so we've been able to monitor him closely now and it doesn't look like the damage is spreading any further.
But yesterday I was walking through the hall and found a pile of hair from another one of our cats. His hair is thicker with more layers so we hadn't known anything was wrong until it all just fell out in a clump. It was like he had rolled over onto his back like cats do and had left his hair behind him when he got up.
Even before that had happened we had begun to suspect the Spot On might have had something to do with it. I looked over the packaging and saw something that said what to do in the event of a problem with humans. But didn't see anything else on a scan. The type is very small and it had been hard enough trying to read the instructions for applying the material. I had had my glasses on that were what I used for reading normal sized type face and even smaller, but the type was not much bigger than this.