Almost certainly an anti-vaxxer; the crossover between anti-vaccine hooey and a lack of belief in germ theory is of course enormous.
My political discussion group got very concerned about ever shaking this guy's hand, because particulate matter is a thing. I actually speculated myself about what he does all the time, since I routinely wash my hands not out of a fear of germs per se but because I have something I don't want on my hands. I bake, for example, and very seldom can you do that without getting dough on your hands.