The prevalence of nickel hyper-sensitivity varies widely in different countries, nevertheless it is the leading cause of contact dermatitis. The presence of nickel in the diet (mainly plant foods) in some nickel-sensitive subjects can provoke/aggravate eczema and systemic contact dermatitis as well as cause extra-cutaneous symptoms (respiratory, gastrointestinal, neurological). These symptoms, correlated to the ingestion of nickel-containing foods and beverages, in nickel patch test positive individuals, defines the so called “systemic nickel allergy syndrome (SNAS)”, a condition successfully treated by oral desensitization. Although numerous studies have investigated the prevalence of contact nickel allergy or addressed the relationship between nickel intake and onset of systemic symptoms, to our knowledge no epidemiological studies have attempted to estimate the prevalence of SNAS. Therefore, we decided to evaluate consecutive patients (1,696), afferent to four allergy units in Sicily, a region of southern Italy, from October 2010 to March 2011. SNAS was confirmed in 98 patients (5.78%) of the 1,696 studied, suggesting that this clinical entity may be an emergent allergological condition rather than an occasional finding. The most common symptoms complained of in our population were cutaneous (51 patients), gastrointestinal (87 patients) and other systemic clinical manifestations (37 patients). Furthermore, 16 out of the 98 SNAS patients (16.3%) presented IgE-mediated food allergy with a statistically significant association (X2=16.950; P<.0001), therefore suggesting underlying cross-facilitating pathways. These findings need confirmation on wider populations but may help allergists to suspect, during common clinical practice, that cutaneous and extra-cutaneous symptoms may be referred to nickel intake and deserve specific in-depth investigation.

Nickel ingested with food can elicit either systemic cutaneous or gastrointestinal symptoms causing a systemic nickel allergy syndrome (SNAS) that can be treated with tolerance by oral ingestion of the metal. It has been suggested that interleukins 2 (IL-2) and 10 (IL-10) are involved in the mechanisms underlying oral tolerance. We evaluated the clinical efficacy of oral desensitization therapy in SNAS consisting in the administration of nickel sulphate. Because nickel allergy prevalently affects women, only female subjects (N = 22) were recruited. Oral nickel desensitizing therapy was associated with low-nickel diet for three months. Before and after therapy, clinical conditions were evaluated, and circulating cytokines IL-2 and IL-10 were measured. After the two-year treatment, visual analogue scale (VAS)scores for symptoms were significantly reduced (p < 0.001). Patients were released by either cutaneous or gastrointestinal symptoms and by tolerating nickel-containing food. At the end of the treatment, nickel oral challenge test was negative in 18 patients, and IL-2 level in the serum was significantly reduced while IL-10 was increased, although this datum was not statistically significant. Our study confirms the clinical efficacy of nickel oral immunotherapy and focuses on the mechanisms triggered by oral tolerance indicating that reduction of IL-2 can be associated with success of oral nickel desensitizing therapy.Allergic contact dermatitis (ACD) is a cutaneous reaction caused by an increased hypersensitivity after a direct contact with chemicals involving cell-mediated immunological mechanisms (1). According to recent data, prevalence of ACD in the adult general population is approximately 30%, whereas that in children is approximately 20% (2, 3). Qualitative and quantitative environmental exposure to sensitizing compounds varies from region to region. Nickel sulphate is generally considered one ofthe most common among substances causingACD (4). Epidemiological studies indicate that it is the number one allergen in frequency of positive patch test reactions both in Europe and in North America (5-7). Prevalence of nickel allergy in the United States has almost tripled in the last two decades, and young patients had significantly higher rates of nickel sensitivity compared with older patients; women also had significantly higher rates of nickel allergy than men (8). Recent data from the European Surveillance System of Contact Allergies showed that 20% of 9871 tested patients were sensitized to nickel, with the highest prevalence in Italy (32.2%) (9).