How to Get Rid of Sagging and Loss of Elasticity of Underarms?

Thank you for your question about removing underarm sagging skin in a non-surgical fashion. That is undoubtedly a multimillion-dollar question. In my experience, there is no definitive way to get rid of excess underarm hanging skin in a non-surgical fashion. There are modalities like radiofrequency and perhaps the Morpheus8 treatments. These treatments are modest at best when it comes to tightening underarm skin. Hopefully, there will be machines like transdermal ultrasound, which will help to melt the fat. Another technique you can consider would be cool sculpting. This is a non-invasive treatment that will help to remove the fat in the arms. I hope my answer helps to describe how to tighten loose hanging skin from the underarms.
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.)

It's not unusual for patients who suffer from loose upper arm skin, to fear the scarring that may be associated with brachioplasty. For this reason, they often seek non-surgical alternatives to this procedure. A variety of options have been utilized including cool-sculpting, laser treatments and exercises in an attempt to tighten loose skin. Unfortunately, none of these alternatives adequately address excess upper arm skin.When sag is mild, liposuction and cool-sculpting may have benefit, but in more severe cases, they have no impact on loose skin. For this reason, brachioplasty is the only viable alternative for treating severe upper arm skin. If you're concerned about this problem, consultation with a board certified plastic surgeon who has experience with this procedure is appropriate. This surgeon should be able to help formulate a treatment plan to address your concerns.

How to Get Rid of Saggy Arm?
Without any photos, it is hard to give you the most accurate advice. The best way to remove underarm sagging would be to get plastic surgery, this is called a brachioplasty. There are different techniques depending on your needs each with different size incision scars. There are non-surgical options like arm exercises, but you will probably not be pleased with the slow and minimal results.