I only worked with these two woods today...and no synthetics, and I got a rash on my neck. It has happened before, but I wasn't able to single anything out as I had worked with too many woods on those days...plus glass and phenolic. 
Today though, these were the only two woods I messed with. Of course I realize everyone is different so it could be either, or even both, but I thought I would ask which causes more issues.
			
			
			
				I get a little weird with wenge but havent work with purpleheart. I've heard of other people being sensitive to wenge also.
			
			
			
				I hate working with purple heart -makes me itch like crazy.
			
			
			
				osage sawdust gives me a nasty rash on my arms. also,sinus infections. don
			
			
			
				Reminds me of poison ivy. Itchy and a slight swelling. Fortunately, wiping down my neck with a damp rag and keeping aloe on it helps a lot.
			
			
			
				I've worked with purpleheart a lot and never had it bother me at all, sure does kill my saw blades though. Never worked with wenge so I cant help you there.
			
			
			
				purpleheart hasn't bothered me when I worke with it. I haven't worked with wenge.
			
			
			
				Neither has bothered me, but I would suspect the wenge,if it is as dry and powdery dust as the stuff I had.
Now yew on the other hand..........
			
			
			
				i have worked with purpleheart and haven't had a problem.  knock on wood
			
			
			
				I would bet on the Wenge but your body will become desensitized to a lot of woods over time and they will start to bother you.  Coco Bolo does'nt bother me but Walnut will make me sick for a week.