Loose skin under arm pit. Any suggestions? (Photo)

This area could be treated with radiofrequency skin tightening like Renuvion or even with micro-needing and radiofrequency.

It's difficult to give a specific recommendation without an exam or further photos, but typically if you have loose skin and not excess fat, surgical removal of the skin is necessary for improvement. The incision can be made in the under arm area so that it is not visible when your arms are down. The next step is to visit with a board certified plastic surgeon near you for a consultation.

Thank you for asking "Loose skin under arm pit."
You have determined your diagnosis accurately. Kybella will not help at this area. Kybella melts fat. It does nothing for the skin. To get rid of skin in this area it must be surgically removed. To fix this problem, I routinely make an incision from the armpit down the side of the chest towards the top of the bra strap line. An elliptical area of skin fat is removed in the armpit region and the skin is less tightened.
Liposuction will not really effect this area because your problem is excess skin, not fat. Liposuction is designed for fatty pockets not excess skin. Therefore the solution to your problem is a vertical torsoplasty or armpit skin reduction. I hope this helps to answer questions regarding what to do with excess skin in the armpit region.
I specialize in arm lifts. I hope that I have answered your questions regarding the arm reduction. If you have any more questions regarding the arm lift, arm reduction, brachioplasty or arm crease fat grafting, please contact my office. Since a brachioplasty or arm lift surgery is a difficult procedure, please seek an experienced, board-certified plastic surgeon with significant experience performing these types of arm lifts. Do your research. Make sure your chosen plastic surgeon has performed at least 100 arm lifts. Make sure they have the before and after pictures to prove it. Carefully examine their before and after pictures and check their reviews on RealSelf.  

Sincerely, Dr. Katzen. (“Verified” Plastic Surgeon, President of the American Society of Bariatric Plastic Surgeons, certified by the American Board of Plastic Surgery, Fellow of the International Society of Aesthetic Plastic Surgery, American College of Surgery, International College of Surgery, and American Board of Metabolic and Bariatric Surgery, and ​member of the American Society of Plastic Surgery, American Academy of Cosmetic Surgery and RealSelf Hall of Fame.)