One thing to keep in mind is not just the "allergen" nature of wood dust but also its "particulate" aspect. Any particles breathed in must then be expelled through coughing; some particles are much harder to expel than others. My grandfather hand-cut leather for work gloves, welding aprons, and other protective clothing for decades. He also smoked like a maniac since he was 13 - up to 4 packs a day before he quit when he was 70. A couple years later he died of lung cancer, but it did not appear to be caused by smoking. He had a form of cancer very similar to the type caused by asbestos - the tiny leather fibers kicked up from cutting "hooked" into his lung tissue and could not be expelled, apperantly causing cancer in a manner similar to asbestos fibers. I do not know enough about different species of wood to comment on specific toxicities, but I would imagine that if it is a species with silica in it, it would be of concern.