Nickel is a very common metal in the environment, especially linked to human industrial activities. He has always been considered the main responsible for contact dermatitis in adults as well as in children. In recent years there has been a considerable increase in these cases and it seems that, beyond contact allergy, foods have an importance in determining the onset of this disorder. This is probably to be related to the contamination of the same foods, during one or more phases of their collection or processing, whether artisanal or industrial. People who are moderately or severely allergic to nickel are more likely to report non-cutaneous symptoms, such as: weakness, nausea and vomiting, headache, tachycardia and shortness of breath. With the persistence of the problem appear gastritis or gastro-colitis, oral mouth ulcers and weight loss. Some mechanisms of gastrointestinal symptoms have been clarified. The nickel ions appear to form a fairly stable complex with the outer portion of the TLR4 receptor (Raghavan B et al., 2012; Zoroddu MA et al., 2014; Peana M et al., 2017) and activate a protein complex inside the cells, called inflammosome. (NLRP3). The TLR4 receptor is distributed at both the cutaneous and immune levels and in intestinal mucosa. It is a sensor for bacteria, proteins, complex substances and cell fragments. It is involved in innate immunity and inflammatory reactions, so its activation in the toxic actions of nickel justifies the symptoms both on the skin and in the intestine.
It is noted that among the foods considered to be high in nickel, there are some undoubted fat consistency such as margarine, seed oils, hazelnuts and other dried fruit. Although it may seem untrustworthy, indeed, the highest concentrations of nickel are found in these, cocoa and cocoa butter included, which are highly caloric. This comes to the topic of the increasingly frequent cases of allergies reported by patients to the consumption of dried fruit and seed oils. In fact, for the production of “hydrogenated” fats, the conversion of mono- or poly-unsaturated fatty acids present in the triglycerides of certain fats requires nickel-based catalysts. It is not excluded that traces of these can pass into the oil in some phases of processing. If it is true that food nickel may represent the real allergen in sensitive individuals, it is not clear what part it plays in comparison to allergies caused by the consumption of vegetable oils, margarines and similar products, which could be contaminated by industrial processing. It is not clear, however, if the allergic symptomatology is due to nickel present in the food itself, since in the case of seed oils there is the possibility that nickel comes from sources of processing. Furthermore, a nickel allergy must be distinguished from that of active protein components of nuts, such as peanuts and hazelnuts.
Beyond its presence in known foods, living organisms contain traces of nickel in the tissues or cells, indicating that it is useful for some enzymatic and biological functions. One of these is being an enzymatic cofactor of pancreatic lipase, a digestive enzyme that has the role of breaking down the fats introduced with the diet. Associations between nickel ions and structure and functions of insulin have been reported in the past, and it seems definitively established that a deficiency may lead to hypertension and / or hypoglycemia. Looking at the list of symptoms that characterize the clinically significant forms of nickel allergy, one can not fail to notice the striking similarity between these and those reported in patients suffering from digestive problems (liver failure, outcomes of chronic pancreatitis, malabsorption or related syndromes). Admitting that nickel is a natural regulator of pancreas functions, tested for the enzymatic-digestive section but not yet confirmed for the endocrine, it is not surprising that the most allergenic and / or richer nickel-rich foods are those with a high fat content (oils and derivatives, cocoa, butter, dried fruit). Coincidentally, they are also those that induce a more energetic pancreatic response, both of enzymatic type and in terms of the subsequent reflex of gastric emptying.
There is no evidence at the moment, but it is possible that nickel allergy actually represents a “spy” for an internist problem that can not be recognized with current diagnostic means. Given the relationship between nickel and pancreas functions described above, it is hypothesizable that to be allergic to nickel would mean an inherent weakness of the hepato-pancreatic system. That this can predispose to diabetes, enzyme deficiencies and other medical complications can not be confirmed at the moment. There is evidence, on the contrary, that demonstrates the possibility of association between sensitivity to nickel and symptoms such as chronic fatigue in relation to the appearance of some autoimmunity. Already in 1999, a possible link between exposure to mercury or nickel was suspected, with patients suffering from indeterminable chronic asthenia. Over the years the suspicions have become more and more, reaching the possibility of linking the sensitivity to nickel with autoimmune diseases. The first case of a patient with simultaneous nickel erythema and autoimmune thyroiditis was published a few years ago (Niedzela M et al., 2012), and further publications reinforce the original hypotheses (Andrioli M et al., 2015). The total role of nickel in immune reactions is not known, but preliminary data indicate that children with early exposure to objects containing nickel are less likely to develop their adulthood allergy.
- edited by Dr. Gianfrancesco Cormaci, PhD, specialist in Clinical Biochemistry.
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