Nickel is a silvery metal pertaining to the group of the iron. There are various types of nickel allergies which can be divided, in a schematic way, into:
1) Allergic contact dermatitis (ACD), that is caused by the contact with nickel. This is easy to identify since it appears like an eczema in the areas that are in close contact with the items that release nickel, such as jewelry or the belt buckle. The nickel allergic contact dermatitis can be diagnosed with a patch test.
2) Systemic nickel allergy syndrome (SNAS), that leads to cutaneous manifestations as well as extra cutaneous manifestations (including those gastrointestinal in nature such as pain, diarrhea, vomit, swelling etc.) One of the causes of this type of allergy is the exposure to nickel via food. The diagnosis is made through oral food challenge tests with the suspect food, following a diet that eliminates the suspect food.
The content of nickel in soil and water is highly variable in different regions of the world, and it varies based on the type of soil, the use of synthetic fertilizers and pesticides, and the soil contamination with industrial and urban waste. This implies that the content of nickel in various foods is equally variable. However, it is important to consider that it is on average four times higher in foods of vegetable origin in comparison with foods derived from animals (meat, milk and dairy, eggs). Worldwide, the average daily assumption of nickel is approximately 0,2-0,6 mg; this quantity is reached mainly through consumption of foods of vegetable origin.
Numerous scientific studies present conflicting results regarding the concentration of nickel in foods, which is most likely due to the large variability of what stated above. Despite this, some food categories are unanimously defined “high in nickel”: peanuts, beans, lentils, peas, soy, oat, cocoa (and chocolate), walnuts, hazelnuts, whole wheat.
It is also important to underline the importance of the content of nickel in water: its concentration in drinkable water is usually low, with the exception of water polluted by natural or industrial sources and of the first water running in the tap in the morning, which is due to the release of the metal during the night. For individuals that have an allergy to nickel it is therefore recommendable to let the water run before drinking it in the morning.
In a normal feeding regime, another element that might make the daily assumption of nickel more fluctuating, and therefore not constant, is the use of pots, pans and utensils stainless steel, especially when they are used new or to cook acid foods.
Nickel might as well accidentally contaminate canned foods, due to a process of erosion of the metal cans. Thus, it is unadvisable to consume foods that are stored in metal cans, for example tuna.
On the contrary it is possible to consume with ease: vegetables such as radicchio, endive, soncino, fennel, eggplant, zucchini, peppers, cucumber, beetroot; some kind of fruit, such as watermelon, melon, citrus fruit, peach, banana, strawberry, grapes; as well as milk and diary, plain flour, rice, meat of all kinds and fish.
It is advisable, as is the case for any allergy or intolerance, to contact a professional competent in the field, to avoid the risk of nutritional deficiencies caused by the exclusion of certain food categories.
Nickel: systemic allergy and diet. Literature review by Silvio Pizzutelli. 2010.
Nickel. Ministry of Health. 2016.
Umberto Veronesi Foundation
Original version of: Federica Mascaretti
Translated by: Elena Briasco