Update on systemic nickel allergy syndrome and diet.

We read with interest the Pizzutelli article on the relationship of systemic nickel hypersensitivity and diet, and find this an extremely immunologically complex and fascinating subject (1). We attempt to further elaborate on the differentiation of systemic nickel allergy syndrome (SNAS) and systemic contact dermatitis (SCD), as well as update the readers on recent developments in dietary nickel avoidance literature. SCD, first described by Jadassohn in 1895, is a subset of allergic contact dermatitis (ACD) in which dermatitis is elicited from allergen exposure via routes other than trans-cutaneous contact (2) (see table 1). Cases have been reported to mercury, sulfonamide antibiotics, cinnamon oil, potassium dichromate, and thiamine, among others, and specifically to balsam of Peru, chromium and nickel following oral exposure (3,4). Nickel is the culprit behind systemic nickel allergy syndrome (SNAS) (3), which is reported to present with a multitude of symptoms, most commonly studied of which is vesicular hand eczema; however, SNAS can also present with generalized systemic (eg: fibromyalgia, headache), respiratory, generalized cutaneous and gastrointestinal symptoms (3).