To understand Bombay Blood Group we must understand the details of blood grouping. When we say someone has blood group A, it means that the person has antigen of type 'A' and antibody of type 'B' in his/her blood. People with AB have both antigen A and B in their blood and no antibodies. People with O blood group have only antibodies A and B and no antigens. However what is not generally known is that all these groups have an antigen H on in the blood as well. There are very few people who do not have this antigen H also in their blood. Instead they have antibody H because of which no other blood can be given to them. -