The bulge above the eye of the needle after blood donation is usually due to the following reasons: 1. Because the needle used for puncture when donating blood is relatively thick, the needle used for transfusion and static spotting takes 7.5 gauge. However, when donating blood, the needle is relatively thicker, about 1 times wider than the diameter of a 7.5 gauge needle, and the needle used for blood donation is a 10-15 gauge needle, which can lead to transient venous bruising after the needle has punctured the vein. 2. After donating blood, pressure should be applied, because the body loses too much blood at once and requires some local pressure. If no local pressure is applied, bulging or tortuous veins or varicose veins may appear in the eye of the needle. 3. If the blood is not properly treated locally after donation, infection of the needle puncture site may occur without disinfection, and bulging may occur after infection.