What is the Best Non-surgical Treatment for Sagging Underarms?

Hello and great question. While we all (myself included) wish that there was a great non-invasive way to treat sagging skin; currently there is not. ALL of the non-surgical procedures will, at best, improve the skin sag. The best way to fix sagging skin is to surgically remove it. In many ways this is the same as a Tailor. If you wanted excess clothing garments taken in, you would need to have the seam taken it. In saying that, lets look at the different non-invasive options. But, first I want to just make sure that you understand that the non-surgical market is a “buyer-beware” market. If it sounds to good to be true or if medical grade offices don’t offer the treatment…there is a definite reason for it! Alright, back to the non-invasive options:Lasers: Lasers have the ability to improve skin color, texture, and to a very slight degree tighten skin.
Peels: Peels have the ability to improve skin color, texture, and to a very slight degree tighten skin. But, peels are chemicals and therefore are not typically used to treat large areas.
Dermaroller/Dermapens: These are (relatively) new products that do slightly tighten the skin.
These are the non-surgical mainstays to help tighten the skin. Again, surgical treatment is the definitive way to “treat” or “cure” sagging skin. Non-surgical procedures will improve the sagginess. but it will still be present and noticeable. And remember this is a “buyer-beware” environment with significant “land-mines”.I hope that helps. Best of luck! 

A brachioplasty is probably what you are looking for to achieve significant results. There are really no effective non-surgical treatments for removing significant skin under the arm. Non-invasive procedures like coolsculpting only address the fat that lies under the skin and over the muscle, it does not do anything to improve excess skin. Laser therapy and other skin tightening procedures show extremely minimal results, if there are any results at all. There is a reason why board certified plastic surgeons do not include this procedure in their practice offerings. It would be best to consult with a board certified plastic surgeon to review the best options for you.

Thank you for your question. There are a number of radiofrequency and infrared devices that use heat to tighten the deeper dermis. This can create some mild skin contraction and tightening. These options usually require multiple treatments to achieve a satisfactory result and then maintenance treatments. And it also depends on how much tightening you need. You may not be a candidate for this at all. 
Liposuction alone removes fat and if you're young and have good skin tone it may contract. 
Most patients are best served by a brachioplasty or arm lift. This can come in a mini version if the defect is minor. The trade off is the scar but the outcomes are more dramatic. 
See a board certified plastic surgeon for consultation to learn what might be best for you.