John K Jordan
>>>a mask is a must for me!
Exactly the same for me. I've been planing, bandsawing, and turning walnut in the last week and I have to wear an industrial 3M respirator with P100 filters or I too get the "flu." My sinuses get clogged then my head aches. With the respirator I have no issues. While turning and sanding I also use a powerful dust collector.
I get no rash, skin sensitivity (as with a couple of other woods) or lung issues.
If I walk through the shop later and can smell the walnut in the air it's enough to cause a problem. I did find if am sloppy and have a head reaction a prescription nasal spray quickly gets me back to normal in a couple of minutes with no aftereffects.
Husking, shelling, and eating raw or cooked walnuts causes no issues for me either.
BTW, the worst wood I've ever encountered is labeled Borneo Rosewood - I still have some but refuse to use it for anything! I checked the Wood Database: "The sap of Rengas is reported to be strongly irritating to the skin, causing blisters, sores, and reactions similar to poison ivy, as well as fever and constitutional effects in some individuals."