The following result is obtained by Our expert's opinion: This also known as hemophobia, it is not directly related to your ancestry. It is mostly caused due to any happening of any event related in your past, childhood or adolescent. It is also caused due to having previous negative experience related to blood. Those who had been through very traumatic injury or illness that caused a major loss of blood are at higher risk. Childhood and adolescent both are every sensitive stage of human life, a person intensely retains what he or she saw at this stage. Hence, if you saw your parents or grandparents had the same phobia, you unusually retain that intensely.Chances of natural heredity of this phobia is also possible.