Nickel-free diet: what is it? How to do it?
To answer this question, let’s see what nickel is and what nickel allergy consists of.

Allergy to Nickel

Allergy caused by nickel is one of the most frequent forms of contact dermatitis.
People who are allergic to nickel (my mother is, for example) generally need to be careful not to wear any jewelry or accessories that contain nickel and lots of clothing. Nickel, a naturally occurring metal in many mineral elements, is similar to silver , and in industry and manufacturing it is possible to find it in combination with other metals or materials, in common alloys which, for example, characterize some of our coins. ‘steel etc.

Depending on the type of allergy, there is a simple contact allergy, so it is good to avoid coming into contact with objects that contain nickel (generally avoid wearing them; however each case is subjective, there are forms of mild intolerance in which it is necessary to avoid rings and earrings or cosmetics and a full-blown allergy in which even steel and other objects should not be touched) and a systemic allergy that is also food-related. 

What is systemic nickel allergy

In the latter case we speak of  Systemic Allergy to Nickel Syndrome (SNAS).
This allergy can manifest itself with many symptoms, but the dermatological ones are the first and most common: then there are others ranging from migraines to various gastrointestinal symptoms such as vomiting or nausea. Now, precisely since nickel is found abundantly in nature, for example in the soil, it is very difficult to make a specific classification of foods that contain nickel in order to avoid them, especially for those of natural origin.