Ultherapy was recommended for under my chin for skin tightening (that is loose skin hanging) will it work? (photos)

Ultherapy is an excellent treatment for firming up support structures. Appropriate candidates should have adequate elasticity so that the superficial skin "follows" the new contour created in the deeper layers by the ultrasound.

Ultherapy will slow the sagging process down but not make major changes. morpheus will start to show you improvement especially if combined with halo and at home dermarolling (see link).
I've been doing twice yearly ultherapy and Thermage since I was 26 years old (im 39 now and look 25).

if you want a dramatic change necklift/facelift, or Facetite + platymsplasty. noninvasive will improve the area and facetite, threads, morpheus, thermage/ultherapy  start at home dermarolling to tighten you skin, see emeragecismetics.com where we do free skincare consults daily and recommend MTS roller with anteageMD ampules daily (see dermarolling package).

With significant neck sagging you would need a neck/face lift with muscle tightening (platysmaplasty). at the same time lasers (fraxel,  co2 or erbium( or microneedling RF (fractora, intensif) can be . performed to improve the crepe skin or wrinkles.  You need a formal consultation, as the neck can be treated with a combination approach:
1. micro needling and lasers for texture
2. botox, disport or xeomin to help platysmal bands
3. intensif or fractora RF microneedling for crepe skin and lifting
4. fillers like belotero, restylane silk, juvederm volbella to improve lines and folds
5. neck/face lifting if sagging is prominent or early starting +/- platysmaplasty (muscle tightening)
6. J plasma/Renuvion, thermiRF, inmode facetite for internal tightening
7. ultherapy and thermage for external tightening
8. regular Venus legacy, exilis ultra, or inmode forma treatments with facials to maintain tightness
9. PDO novathreads or silhouette instalift cone threads for lifting and long-term collagen production
see an expert for a full evaluation and treatment plan based on your individual situation and goals.
Best, Dr. Emer