I think that the change itself is morally problematic absent some disease. Therapy means that something is broken as compared to the divine design. For example, a heart valve is not where it is supposed to be. Cosmetic is when the human parent wishes to alter the design alrady given the child, for example stature or eye color.
When a human being is groomed, e.g. receives a hair cut or a shave, there is no interference in the design. God gave us tools with which we groom out children or ourselves.
It is sinful to interfere in the act of creation. It is not sinful to remove and obstacle, such as a disease, even on some stage of creation, or to alter appearance of the finished product, such as grooming.
remove and obstacle -> remove an obstacle