There are various synonyms for the phrase "in skin", depending on the context in which it is used. One common synonym is "underneath the skin", which refers to something that is situated or located below the surface layer of the skin. Another synonym is "within the skin", which conveys the idea that something is located inside the skin, such as a tattoo ink or a medical implant. "In the flesh" is another synonym that can be used to describe something that is physically present in or on the skin. Other synonyms include "on the surface", "at the skin level", and "in the epidermis", each of which describes something in proximity to or occupying a particular layer of the skin.