The Role of NIchel and LTPs Sensitization in Functional Gastrointestinal Disorders: the NILT Study

Non-specific lipid transfer proteins (nsLTPs) are currently recognized as the most prevalent cause of primary IgE-mediated food allergy in Mediterranean populations and constitute a leading trigger of anaphylactic reactions. In Italy, the prevalence of LTP sensitization is estimated at 2-2.4% in adults and approximately 9% in children, with marked geographic variation. Specifically, higher prevalence rates are observed in central and southern regions and on the islands (21.3%-27.2%) compared to the northern regions (approximately 11%). LTPs are ubiquitous panallergens, widely expressed throughout the plant kingdom. They represent the major allergens within the Rosaceae family in individuals not sensitized to birch pollen and have also been identified and characterized in numerous plant-derived foods, including nuts, legumes, rice, maize, beer, spelt, and wheat. The clinical spectrum of LTP hypersensitivity is highly heterogeneous. While a significant proportion of sensitized individuals remain asymptomatic, others may present with localized reactions such as contact urticaria or oral allergy syndrome (OAS). More severe cases may involve gastrointestinal symptoms (e.g., vomiting, epigastric discomfort, abdominal pain), cutaneous and respiratory manifestations, and systemic responses up to anaphylactic shock. Nickel is a ubiquitous metal employed in a wide range of industrial applications and consumer products, including stainless steel, metal plating, various alloys, and inexpensive jewelry. It is also naturally present in both animal and plant-based food sources (e.g., cereals, cocoa, legumes, fresh fruits and nuts, fish). Nickel is the most common sensitizer in allergic contact dermatitis, affecting approximately 20% of the general population and around 10% of the pediatric population. Sensitization to nickel involves a delayed-type (Type IV) hypersensitivity reaction and is not IgE-mediated. Clinical manifestations range from localized allergic contact dermatitis to systemic involvement, referred to as systemic nickel allergy syndrome (SNAS), which is characterized predominantly by gastrointestinal symptoms, although respiratory and other systemic manifestations can also occur. Gastrointestinal symptoms such as gastroesophageal reflux disease (GERD), functional dyspepsia, abdominal pain, and altered bowel habits, when not associated with overt allergic signs or underlying organic disease, are typically classified as functional gastrointestinal disorders (FGIDs). Several studies report that up to 40% of adult patients with FGIDs exhibit nickel sensitization; however, data in the pediatric population remain scarce. Chelanik® is a dietary supplement designed to support individuals with nickel hypersensitivity. It contains bioactive components purported to exert immunomodulatory and anti-inflammatory effects. Nevertheless, in vitro human data directly demonstrating its activity on lymphocyte function are currently lacking. This prospective, experimental, single-center study aims to determine the prevalence of sensitization to LTP and nickel among patients presenting with functional dyspepsia or irritable bowel syndrome (IBS), and to assess in vitro the potential immunomodulatory effects of Chelanik® on peripheral blood lymphocytes from individuals with nickel allergy.