Toxic mold is a common problem, especially in foggy areas along the coast. As a general rule, anytime you have water coming in contact with cellulose (e.g., drywall or fiberboard) for more than 24 hours, you have a mold infestation. Fog alone will not do it, but fog will very much slow drying and aggravate an existing water spill or leak.
There are literally thousands of types of mold spores floating around, of which a few have been studied and found to be quite toxic. Aspergillus/Penicillium, Chladosporium and Stachybotris are the best known of the toxic molds. They produce problems in two ways: their spores - seeds, essentially, which float around - produce allergy symptoms, their mycotoxins - waste products, which also float around - poisoning at the cellular level. One of the mycotoxins of this group is related chemically to Sarin nerve gas, another is listed in the Army Field Manual as a biological warfare weapon.
Not the kind of stuff you want floating around in your house.
Toxic molds can produce a wide range of symptoms.
Treatment includes getting a mold specialist out to find pockets of mold in your house (which then need to be remediated by a professional), improving liver excretory function, binders to minimize reabsorption of mycotoxins from bile, and other modalities which depend on the individual situation.
Mold exposure seldom occurs in isolation, so attention to the other patient-specific issues is also important.