Hi, thank you for asking Healthcare Magic I have gone through your query and understood your concerns. There is no evidence directly linking mold exposure to heart murmur. Molds can trigger asthma symptoms in people who have allergies. This might be the case with your son. A heart murmur can result when the heart is normal or abnormal. When the heart is normal, it is called an innocent murmur. This occurs when blood flows more rapidly through the heart. Conditions that could be at the origin of this murmur in your son include physical activity or exercise, fever or anemia (shortage of red blood cells). Although most heart murmurs aren t serious, some may result from a heart problem. The most common cause of abnormal murmurs in children is when babies are born with structural problems of the heart (congenital heart defect). To diagnose this condition, an ultrasound of the heart is necessary. I would suggest your see a pediatrician or pediatric cardiologist for proper assessment. I hope that helps. I wish him good health