We all need to keep some perspective on health and safety issues but it is a fact that all timbers are liable to cause an allergic reaction of some type to some people.
This may vary according to exposure time but it is sensible to protect and reduce the risk to your eyes, face, respiratory system and maybe your skin, by the best means you have available.
Spalted timbers may contain the spores of fungi and bacteria at work, so take especial care when working with these timbers, especially when using abrasives.
The Wood Database makes interesting further reading for those with an interest in safety and ecological issues.