Q. Does Judaism allow alterations to one’s skin, e.g. body piercing?
A. Tattooing is viewed negatively as its origins were idolatrous (Lev. 19:28; Maimonides, Hilchot Avodah Zarah 12:11), even though, technically speaking, it is banned only if done with indelible ink and in the form of writing (Makkot 3:6; Shulchan Aruch, Yoreh De’ah 180:1).
Cosmetic surgery raises the halachic issues of intentionally wounding oneself, risking infection, etc. Rabbinic responsa permit it for psychological or medical reasons (e.g. after an accident) but not for mere vanity, especially among males, unless the operation is common practice in the place concerned (see I Jakobovits, “Jewish Medical Ethics”).
Piercing the ears was a mark of servitude in Biblical times (Ex. 21:6), yet ear- and nose-rings were often worn by women. For men to wear them would presumably infringe the prohibition against cross-dressing. The problem today is that some people insert rings in strange parts of their person as a mark of vanity or frivolity. Even if what is done is not likely to be hazardous to health, vanity or a sense of fun is no justification for immodesty - or for meshugass.
The basic rule is that the body is the property of the Holy One, blessed is He, and its dignity must not be compromised or its integrity invaded. Instead of overdoing the preening of the body, one should work on one’s mind, heart and soul.