as others have mentioned, exotic wood dust can be a real issue. I make a lot of knife handles and have experienced blisters in my nose from sanding cocobolo, rosewood, bubinga, paduak, ,etc. Even when wearing a dust mask, just enough dust/oil gets by the seal around the face to cause the problem. Everyone has a different level of "allergic" reaction and I've found I'm pretty sensitive. I've had to put the shop vac's nozzle right up to the piece being sanded to prevent problems. However, I'm not allergic to my wife's cats...darn!