I am 18 years old and have an extremely saggy neck. It’s majority skin, not fat. It is not even a double chin, just extra skin.

Dear Calm,
The anatomy dictates the treatment, not your age.
I suggest you research MyEllevate, a minimally invasive, non-incision suture suspension neck lift. With an in person consultation, you can get an idea if your degree of skin laxity is amenable to correction with this procedure. The suture pulls the loose skin up into the cervicomental angle and under the border of the mandible. This provides definition by tucking the loose skin up under the mandible.

Thanks for your question. There are several very effective treatment options for treating neck skin laxity. In non-surgical aesthetics, skin tightening is going to be "all about heat delivery". This is because the microinjury of heat is needed to stimulate collagen and elastin production in the skin, which happens during the healing response to the treatment. Results from any of these procedures are not instant but rather develop gradually over the course of 3 to 6 months:
1. Sofwave- utilizing microfocused ultrasound to deliver heat to the deep dermis at a depth of 1.5mm, generating new collagen and elastin in the skin. The number of pulses delivered is important- the more laxity there is, the more important it is to do the ‘advanced protocol’ with 4 full passes. Most will need 1 to 2 sessions spaced 4 or more weeks apart. You should have either ‘full face and neck’ or at least ‘lower face and neck’ to get the best result for the jawline. Sofwave has no effect on fat cells as the energy cannot reach that level. Numbing for he procedure is primarily topical.
2. Morpheus8- utilizing RF energy delivered at the tips of micropins. With this approach you get the collagen stimulation of the heat PLUS the collagen stimulation of the microneedling, so you can potentially get more result per session, but at the expense of 'some downtime'- puffiness, faint redness for a day or two, potential bruising. The needles can also be set deeper in certain regions so that they will destroy unwanted fat cells- such as in the jowls and the “double chin” zone. Most will need 3 sessions- can be spaced 4 or more weeks apart. ‘Full Face and Neck’ is the ideal approach. Numbing for this procedure is primarily topical but nerve blocks (injection numbing) is very helpful also.
3. FaceTite- this procedure involves placement of a probe just under the skin to achieve full thickness heating. The probe is introduced through some simple needle pokes- considered ‘minimally invasive’. Most require a single session. Results typically last 5 years. Numbing for this procedure requires lidocaine injection.

At your age many times skin laxity can be improved with non surgical options but an evaluation is needed to determine what is recommended. Options can include FaceTite, Morpheus8, InMode, and more. We also recommend using medical grade skin care products like Transform MD and wearing sunscreen every day.