Science Common Sense

106 - Why do we have different blood types?

We have different blood types because of the way our bodies defend against infections. Our blood has special parts called antigens that help keep us safe. Antigens are like flags that tell our body, "This is me, don't attack me."

There are four main blood types: A, B, AB, and O. Each type has different antigens. For example:

• Type A blood has A antigens
• Type B blood has B antigens
• Type AB blood has both A and B antigens
• Type O blood has neither A nor B antigens

When you get a transfusion (get blood from someone else), your body checks if the new blood's antigens match yours. If they don't match, your body might think the new blood is an enemy and fight it. That's why we need to match blood types when someone needs a transfusion.