For how long would it take to develop swelling from a flu shot if you had a mastectomy on that side?

Post-mastectomy . If the mastectomy also took lymph nodes out of the armpit, the arm will always have a tendency to swell. You should avoid shots, blood drawing, blood pressure on that arm to try to not have swelling. If your arm is swollen, you can try elevating it over your head. Sleep with it up on a pillow. If swelling continues, your doctor can prescribe a fitted sleeve to help keep swelling under control.