- Chemical intolerance to food, food additives or drugs leading to symptoms of fatigue, headaches, rash, mood changes, and “brain fog” is most commonly initiated by exposure to toxic mold (after floods or hurricanes), followed by pesticides, medical procedures and remodeling/ construction. https://enveurope.springeropen.com/articles/10.1186/s12302-023-00772-x 8 comments science