LONDON — People measure adulthood by an ever-shifting set of age limits for rights like driving, drinking, voting, having sex, marrying, or serving in the military. Add another to the list: How old must you be to get your tongue or an “intimate” body part pierced?

In Wales, the answer is 18, under a law that took effect on Thursday, just days after the Welsh government proposed allowing people as young as 16 to vote in local elections. The restriction on piercing, part of a health law that passed last year with broad support in the Welsh National Assembly, prohibits piercing the tongue, breast, genitals or posterior of anyone younger than 18.

There are basic standards that apply across Britain. The law prohibits piercing the genitals of anyone under 16, the age of sexual consent, or the nipples of a girl under 16. In England, there is no age limit for piercing tongues, boys’ nipples or less intimate body parts. In Scotland, any piercings, even of earlobes, require parental approval before age 16.

The Welsh law was prompted by studies and surveys reporting that not only are young people far more likely to have piercings, their piercings are much more likely to cause problems like infections and, in the case of tongue studs, damaged teeth.