I love this forum!!
Last 2 companies I flew for had strict policies about living the flight deck clean and tidy. Neverless our "office" appeared always to be in need of of a good cleaning. I think it's just staying hours in the same seat, eating, writing, reading and sometimes sweating.
I personally don't feel too much unconfortable about this. And it's years I don't get a serious cold or any similar contagious deseases. Did I become immune? Did I get a benefical effect by staying exposed to millions of germs my collegues spread?