
It grows on wood and paper (like the paper covering over wallboard) and it is the mytotoxins produced by the mold that cause trouble, generally in the form of typical allergic reactions; i.e., runny nose,
sneezing, runny eyes, etc. Here is a web page about stachybotrys and resulting symptoms: http://www.idph.state.il.us/envhealth/factsheets/stachybotrys.htm
As with any allergy or toxic reaction, once the patient is removed from the irritant, rapid improvement is generally seen.