4 weeks after BBL, lower back and belly is itchy and painful, when will this go away? (photos)

Itching is fairly common after surgery.  If there is any sign of rash or allergic reaction, that would be something different.  My patients choose to wear a cotton t-shirt under the garment to lessen the itching.  I would try to email or call the surgeon.  Surgeons want to know about potential problems.Kenneth Hughes, MD, Board Certified Plastic SurgeonLos Angeles, CA

This is a great question and one that we always discuss with our patients before surgery. A BBL is such a great procedure but the recovery happens in stages for sure (in most of my patients at least). The initial phase is just the post op discomfort which typically lasts just a few days. Then the bruising and swelling stage with the bruising revolving in a couple of weeks and the swelling resolving almost completely in a few months. Everyone is different and heals different but this is typical. 
Itching is also fairly common and is a function of the healing process, unless you are having a rash or a reaction to your garment, tape, or something else. It also tends to improve with time and massage and sometimes with Benadryl. Always discuss with your surgeon your symptoms and any medication you plan on taking and if you feel like there is any issue with your healing process. I'm sure he or she will want to know so they can help!
I hope this was helpful.
Good luck and good health!

The photos are a bit dark, and itchiness can be from many different sources including normal healing and a rash. You are best to be seen in person.  If the garment is too tight,. you may need an alternative garment.