I read this thread this morning. This afternoon I routed some dados in a walnut panel. I was so absorbed in getting the dados lined up correctly, I didnt think about protecting myself from the dust. I was sitting directly in the line of fire and got covered with chips and fine dust from the router. I quickly vacuumed up the mess and put on a dust mask for the remainder of the job. When I finished, I tossed my clothes in the laundry basket and showered. I've been waiting in anticipation all evening to experience bad effects from my stupidity. So far, nothing. If I'm going to have a reaction to the walnut, how long does it take to develop?