Having a universal blood type can save a life—either yours or someone else’s—in an emergency. Only about 7% of people are O-, and their blood bank donations are in high demand because this type is used most often for those in need of a transfusion.
This article explains how blood typing works. You will learn what it means to be a universal blood recipient or a universal blood donor. You will also find out why blood types need to be compatible, and what happens if they are not.
Blood Types
To understand how universal blood donors and universal blood recipients work, you need to know the meaning of two key terms: antigens and Rh factor.
Antigens
Antigens are a substance that the body’s immune system can respond to. Antigens are found on the surface of blood cells. When the immune system detects an antigen that it does not recognize, it will fight it.
The antigens on blood cells determine how a recipient reacts to a blood transfusion. The presence or absence of antigens helps categorize the different blood types.
In addition to the universal recipient type, there are seven blood types: O positive, O negative, A positive, A negative, B positive, B negative, and AB negative.
Here are a few key points about blood types and antigens:
If you have blood type A, you have an A antigen. If you have blood type B, you have a B antigen. If you have an AB blood type, you have both A and B antigens. Since a person has all of the antigens that are possible, this blood type is the rarest. If you have type O blood, you have no antigens. O negative blood is considered the universal blood donor type because it is compatible with type A, AB, B, and O positive blood.
Rhesus (Rh) Factor
Blood types are described as being positive or negative. This is based on the presence or absence of a protein called the rhesus (Rh) factor. It’s often written as “+” (positive or present) or “-” (negative or absent) when noting a person’s blood type.
Here’s how the Rh factor affects blood donation:
Rh-negative blood can be given to Rh-negative patientsRh-positive or Rh-negative blood can be given to Rh-positive patients
Since both A and B antigens are present in a person with AB+ blood and it has a positive Rh factor, the recipient will not reject the blood. That means a person who is AB+ is the universal recipient, as they can get any type of blood.
Blood Transfusion Reactions
A person can have a reaction to a transfusion if they receive the wrong type of blood. An allergic reaction to a blood transfusion is also possible, regardless of a person’s blood type.
A hemolytic transfusion reaction is when there is a mismatch between the donor and recipients’ A, B, and O blood types. Antibodies in the recipient’s blood attach to the donor’s red blood cells and destroy them in the recipient’s bloodstream, liver, and spleen.
The body’s response can cause a person to have a yellow tint to their eyes and skin (jaundice). It also can cause uncontrolled clotting in the bloodstream, shock, and rarely death.
Acute vs. Delayed Reactions
Blood transfusion reactions are divided into two categories: acute and delayed.
Acute reactions happen within 24 hours of a transfusionDelayed reactions come later, and may happen two weeks to 30 days after a transfusion
Hemolytic reactions are rare because hospital blood banks type and crossmatch each unit of blood to be given to a recipient.
Allergic Reactions to Blood
An allergic reaction to a blood transfusion is also called an acute non-hemolytic transfusion reaction.
This type of reaction is not caused by a blood type mismatch—it happens because the recipient’s body identifies the donor blood as a foreign invader and destroys the cells.
The symptoms of an acute non-hemolytic transfusion reaction include:
ItchingFeverChillsSkin rash
The symptoms of an allergic reaction often go away in a day or two and can be treated by stopping the transfusion. A person can also be given an antihistamine (like Benadryl) to help with symptoms.
If a person has a severe reaction to a blood transfusion, they may need to have more careful screening for blood in the future to prevent a similar reaction during later transfusions.
Organ Donation
Receiving a blood transfusion is not the only time being a universal blood recipient or universal blood donor matters. It also makes a difference when an organ transplant is needed.
A patient who needs an organ and has AB+ blood can accept an organ from donors of all blood types, just as they can accept a blood donation of any type. However, the process of matching an organ donor with a recipient is more complicated than only matching a blood type.
The organ allocation system is set up so that it’s fair to people waiting for a donor organ. This way, people with AB blood don’t receive more organs than people with other blood types.
Summary
Universal blood donors and universal blood recipients are unique.
A person with a universal donor blood type can give blood that any person can receive. A person with a universal recipient blood type can get any blood donation, which can be life-saving in an emergency.
If you have the universal donor blood type, you know that giving blood can help a lot of people. That said, donating blood if you can is valuable no matter what your blood type is.
Usually, there is enough donated blood to help anyone who needs it; however, there can also be blood product shortages. Ongoing blood donations keep the supply stocked to help all patients in need.
