What is a unique feature of type O blood?

Type O blood is recognized as the universal donor due to its unique characteristics. This distinction comes from the absence of A and B antigens on the surface of the red blood cells in type O blood, which means it can be safely transfused to individuals with any other blood type without triggering an immune response. When any blood type receives type O blood, the recipient's immune system does not recognize it as foreign because there are no antigens present that could cause a reaction. This universal compatibility makes type O blood especially important in emergency situations where there may not be time to determine a patient’s blood type.

In contrast, while type O blood is indeed the most common blood type in many populations, it is not the rarest. It also does not feature the highest iron content among blood types, as the iron content does not vary significantly between different blood types.