I am 65 years old and i just received my flu shot! two days later, i removed my band-aid and i noticed a medium sizedrash. why could it have happened?

Bandaid rash!: Please remove your bandaid sooner to avoid this rash. The bandaid should be removed in the car as you leave the doctor's office unless you have a bleeding disorder. Trapped moisture and the adhesive in the band-aid often cause this reaction. If it doesn't resolve in 2-3 days, consult your doctor.

Probably benign: This could be a reaction to the adhesive on the band-aid or a low-grade inflammation due to your body reacting to the immunization. Generally these are self-limited and resolve without intervention.

Irritant rash: The bandaid, its adhesive, or trapped moisture may have irritated the skin. It is unlikely to be due to the flu shot itself. I discourage bandaids for this very reason. In addition, skin thins as we age and may actually tear as the bandaid is pulled off. Next time request no bandaid (compress the injection site with cotton ball) or coban, a stretchy non adhesive wrap. Remove within 1 hour.