What is the reason why direct relatives cannot donate blood to each other?
Nov 07, 2025
Source: Cainiu Health
Dr. Liu Feng
Introduction
The reasons why direct relatives are generally not recommended as blood donors include a higher risk of graft-versus-host disease, the presence of identical recessive blood group antigens, increased risk of immune rejection, and the potential transmission of genetic diseases. White blood cell antigens in blood from close relatives are highly similar to those of the recipient; after transfusion, donor lymphocytes may not be readily recognized and eliminated by the recipient's immune system, and instead may attack the recipient's tissues and organs.
Direct relatives are generally not recommended as blood donors due to several reasons, including a higher risk of graft-versus-host disease, the presence of identical recessive blood group antigens, increased risk of immune rejection, potential transmission of genetic diseases, and difficulties in ensuring blood quality. A detailed analysis is as follows:
1. High risk of graft-versus-host disease: White blood cell antigens in the blood of direct relatives are highly similar to those of the recipient. After transfusion, donor lymphocytes may not be effectively recognized and eliminated by the recipient's immune system. Instead, these cells may attack the recipient’s tissues and organs, leading to severe graft-versus-host disease, which has a high mortality rate.
2. Presence of identical recessive blood group antigens: Direct relatives may carry the same recessive blood antigens, which are often undetectable during routine blood typing. After transfusion, these antigens may stimulate the recipient to produce antibodies, triggering hemolytic reactions and damaging organ functions such as the kidneys.
3. Increased risk of immune rejection: Even with compatible blood types, the immunologically active components in the blood of relatives are highly similar, potentially causing abnormal immune responses in the recipient. This increases the likelihood of immune rejection, compromises transfusion efficacy, and may lead to adverse reactions.
4. Potential transmission of genetic diseases: If a direct relative has an inherited blood disorder or carries pathogenic genes, these conditions or genes may be transmitted to the recipient through blood transfusion. This could result in new infections or increased disease risk for the recipient, posing long-term health threats.
5. Difficulty in ensuring blood quality: When direct relatives serve as donors, psychological stress due to concern for the recipient or undiagnosed health issues may affect blood quality. Additionally, family-directed donations might bypass strict blood screening procedures, increasing safety risks.
During blood transfusion, the recipient’s vital signs should be closely monitored. Any discomfort such as fever, chills, or rash should be immediately reported to medical staff. After transfusion, follow medical advice for follow-up examinations to ensure there are no abnormal reactions.
