Oral intake of nickel (Ni) is capable of causing the onset of systemic disorders in patients with Systemic Allergy to Nickel Syndrome (SNAS), an emerging allergic condition. Given its ubiquitous age, it is not possible to completely eliminate Ni and, therefore, it is necessary to plan a low-content diet. However, due to various factors (such as variability of Ni concentration in the soil, individual foods, variability of dietary habits and daily menus, different intake of Ni contained in the water, different intake of kitchen utensils, simultaneous intake of other substances), a restrictive diet is difficult and socially discriminating with a strongly negative impact on the quality of life of these patients.

Hydroponic agriculture in a completely controlled, aseptic, artificial, soilless environment could be an alternative for patients suffering from SNAS with known and lower concentrations of metals than those deriving from conventional agricultural techniques, which are affected by the soil of origin and practices cultivation.

The primary outcome of the study is to evaluate the possible effects of taking tomato puree deriving from hydroponic agriculture compared to tomato puree from conventional cultivation in the subjective control of SNAS symptoms, in patients following a low-diet diet.

This is an interventional, randomized, double-blind, single-center crossover study involving a cohort of SNAS patients following a low-nickel diet for at least 4-6 weeks.

Inclusion Criteria:

• Patients with documented diagnosis of SNAS: a) history of SNAS (coexistence of typical skin symptoms and gastrointestinal symptoms); b) positive nickel sulphate patch test; c) clinical improvement of at least 70% after 4-6 weeks of low-nickel diet; d) positivity of the oral challenge test with nickel sulphate.
• Age between 18 and 65 years.
• Written informed consent to participate in the study.
• Patients who are able to participate in all study procedures and to accept and comply with all study needs throughout the study, including the availability of suitable transportation and the time required to undergo all procedures. planned visits.

Exclusion Criteria:

• Women who are pregnant or breastfeeding.
• Patients diagnosed with organic diseases capable of affecting gastrointestinal symptoms (eg celiac disease, poorly controlled diabetes, scleroderma, chronic inflammatory bowel diseases). Lactose intolerance is not an exclusion criterion if the diagnosis has been made for more than 6 months and if the patient does not report adequate symptom relief after at least 6 months of a lactose-free diet.
• Patients who have been taking systemic probiotics, antibiotics or systemic corticosteroids within the past 30 days.
• Patients who have been taking antidepressant or anxiolytic drugs for less than a month. On the other hand, patients can be enrolled who have been taking the aforementioned drugs at a stable dosage for at least one month.
• Patients who abuse coffee, tea, coca cola and with a smoking habit.
• Patients with pacemakers because they cannot be subjected to bioimpedance analysis for the assessment of body composition.

The study product and the comparator product are provided in identical packaging, the labeling shows the randomization number which, however, only the Outcomes Assessor is able to refer to the type of treatment assigned. The organoleptic characteristics of the two products are as similar as possible. The instructions given to patients regarding the preparation and consumption of the products are the same for both products.