Why is Alloderm bulging out of the side and causing me pain? (photo)

It seems like you must have had a revision breast surgery utilizing Alloderm which may have been to help with support or soft tissue weakness, or for rippling, or for capsular contracture. Although you may have to live with the bulging, the pain may be an infection problem.  You should see your plastic surgeon.  

I would guess that you has a revision with the placement of alloderm. You should make an appotinment to see your surgeon. If the alloderm did not get incorporated by your body it could be floating and not holding the implant in place. It looks like you might have had this placed to improve the medial border of the breast. It may have been anchored down medially and perhaps the sutures came loose and that has allowed the alloderm to be free on the edge and the implant to be more palpable.