What Causes Small Itchy Bumps On The Shoulder After Shoulder Replacement?

I am considering reverse shoulder replacement in three weeks. I am experiencing a skin flare up such as small red bumps which itch,and itch. They usually start in the scalp and down the back of me neck. They appear randomly. This time they started on my left leg, then right arm. I have used Aveeno in the past which eventually calms them down. Three similar spots were removed and tested positive for squamous cell carcenoma; on right calf, upper back, and left shoulder. Each surgery was a year apart. All about 1/2 x. 5/8 These bumps feel like there is fluid in the swelling, could they cause some possible danger for infection for this surgery. Thank you,,ken