Type O blood is also one of the blood types. Because blood types can be divided into A, B, AB and O, O blood type contains neither A nor B antigens on the surface of red blood cells, and is commonly known as the universal blood transfusion. However, because the plasma contains anti-A and anti-B antibodies, it may cause the recipient to have different degrees of red blood cell hemolysis. Therefore, type O blood cannot be transfused to other people arbitrarily. RH-positive blood type O cannot be transfused to any RH-negative blood type, and only a small amount may be transfused to any RH-positive blood type. However, people with blood type O are not allowed to receive blood transfusion from other blood types, as this may easily lead to hemolytic reactions.