Can Canker sores be caused my mold? Recently, a family member came over to my house and pointed out that I had mold (black or dark mold) in the crevices of all my windows in my apartment. Before i had been made aware of this, my son had been experiences over the year that were not normal. First, he fainted. Later we found out he had asthma. He has acne. And finally, he had been getting canker sores in his mouth. Had all of this been caused by the warm, moist black mold infested place he called home?