First, I need to take issue with your statement that fleas are no more than a nuisance. Before I learned of DE I lost some cats, puppies and even a mature dog to fleas. They can be a serious menace. My control of choice (and the only one that really works) is DE sprinkled on the floor and rubbed into the fur of the cats and dogs. The dust is a minor annoyance. I have found that after sprinkling the floor if there is a serious infestation, the the fleas go berserk. I wonder if the damage being done by the DE causes a feeding frenzy.
In regard to the problems Judy Hatfield was having. I used to work for a manufacturer of agricultural chemicals. As such I was around Bifenthrin, another pyrethroid derivatve. Occasionally someone would get exposed to some of the chemicals. For the Bifenthrin, the effect was tingling of the exposed area for a couple of days. But, it took a significant amount. A little splashed and wiped off didn't cause a reaction. I never heard of anyone having respiratory reactions, although we inhaled enough of it. The point is, I doubt Judy's problem was due to the pyrethroids. It is my guess that the problem was the boric acid (as listed in the MSDS) or perhaps the illegally applied chemical contained solvents or surfactants that were not listed for home use. Some of them are a more serious problem the active ingredient. Unfortunately, since we don't know the product applied, we cannot reference the MSDS and find the answer. With that information, there may have been a specific remedy that would have solved the problem economically. There is a reason pesticide applicators are licensed and regulated.