Marty Milkovits replies: Many of the tropical exotics contain resins that are irritants to the mucus membranes and respiratory system. In fact OSHA considers air-born wood dust above a certain level to be a carcinogen. Of all the ones that are commonly used, I have found that the fine dust from cocobolo to be the most irritating. In fact it is the only wood that I have any reaction too, including poison ivy.