Nickel is a highly sensitising metal with an almost ubiquitous distribution that can cause both eczematous skin manifestations such as ACD and, with coexisting ACD, clinical pictures with systemic involvement, such as urticaria, angioedema, erythema, pruritus sine materia and gastrointestinal disorders, called systemic nickel allergy syndrome (SNAS).
Nickel is contained in a large number of everyday objects.
Significant amounts are also contained in various foods, and it is precisely nickel ingested in the diet that is responsible for the onset of systemic nickel allergy syndrome.