There has been renewed concern about problems of exposure of the skin to Nickel.
Nickel is used in guitar frets and also in some guitar strings.
There are warnings that prolonged contact with nickel can cause allergies or other medical problems.
However no official body appears to be actually saying that nickel should not be used in guitar components.
Here is a link to a European Chemicals Agency document on ths subject.
As a player I am not sure that I do make continuous contact with my guitar frets or even contact them at all during playing. I know some players with different styles and techniques may have more contact than I do and so I would recommend that they consider the risks for themselves. To avoid the risks they can change their technique/style or else have a guitar made (or re-fretted) with nickel free frets. We have arranged twice for a customer of ours.
As for strings: the windings on classical guitar bass strings are typically described by their makers as silver-plated copper, and in some cases pure silver. As players’ fingers are typically in much greater prolonged contact with strings than with frets, we have asked the makers of the strings we sell to give us information on their nickel content (if any). When we get more information we will update this article.