Hollow cheeks and why they appear
Cheeks hollow when the fat compartments of the face lose volume, which leaves a deflated, tired look below the cheekbones. It is a normal part of ageing, and the loss of collagen that comes with it lets the remaining tissue sit lower, which also deepens the folds from nose to mouth.
There are two ways to put structure back. A hyaluronic acid filler restores shape on the day and can be dissolved. A collagen stimulator such as Juläine or Sculptra builds it gradually over months (Juläine vs Sculptra compares them); Sculptra's UK instructions list the cheeks, and a practice at UNTIL Marylebone publishes Juläine for the midface and cheeks. PLLA treatment in London explains how the slower route works.