What is an ABO incompatibility reaction?

An ABO incompatibility reaction can occur if you receive the wrong type of blood during a blood transfusion. It’s a rare but serious and potentially fatal response to incompatible blood by your immune system.

These reactions are extremely rare, because doctors are aware of the danger of using the wrong blood during a transfusion. There are many precautions in place to reduce the chances of a mistake. Your doctor and nurse know to look for certain symptoms during and after your transfusion that might mean you’re having a reaction. This allows them to provide you with treatment as quickly as possible.

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The four main blood types are A, B, AB, and O. If you’re type A, your red blood cells have proteins attached to them known as A antigens. Type B blood cells carry B antigens. Type AB blood has both A and B antigens, and type O blood has neither A nor B antigens.

Your immune system will produce antibodies against any blood antigens you don’t have in your own blood. That means people with type A blood create antibodies against B antigens. A person with type A blood receiving a transfusion of type B or AB blood would have an ABO incompatibility reaction. In an ABO incompatibility reaction, your immune system attacks the new blood cells and destroys them.

If you have type AB blood, you have both A and B antigens. This means you’re a universal recipient and you can receive any type of blood. However, you can only donate blood to other people who have type AB blood.

If you have type O blood, which has no antigens, you’re a universal donor. You can give your blood to anyone without triggering their immune system, but you can only receive type O blood.

Before a blood transfusion, your doctor will test your blood to determine your blood type. A small sample will be crossmatched with some of your donated blood. The two samples of blood are then mixed and watched for a reaction. This allows your doctor to be certain an incompatibility reaction won’t take place.