Arm itches 2 days after flu shot?

That's OK: Every vaccine is intended to get your immune system's undivided attention. When it does, you get a little inflammation at the site (a sign the vaccine is doing its job), and sometimes that inflammation can precicipitate an itch. If there is a little redness, that's ok, a lot of redness, or a spreading rash, should probably get you to see your doctor.

Happens a lot.: Pain, redness, swelling or itching at shot sit happens frequently. Symptoms usually resolve within a few days.