A study conducted by UniTS professors Luca Cegolon (also working at ASUGI Hygiene and Preventive Medicine Department) and Francesca Larese Filon (ASUGI Occupational Medicine Department) has just published in the international scientific journal Contact Dermatitis (Wiley). The researched was focused on contact allergy to 5% nickel sulfate in 31,948 patients who underwent patch tests in Triveneto from 1997 to 2023.

Nickel is the most frequent cause of contact allergy, a hypersensitivity that can develop after repeated and prolonged skin exposures to allergens.

In 1994, EU Directive 94/27/EC restricted the use of nickel in jewellery and other consumer products that may come into contact with human skin.

Although this measure has led to a progressive reduction in nickel awareness in Europe, the benefit has mainly been seen in younger generations. Older people, on the other hand, who were sensitised before the entry into force of the Directive, contribute to the prevalence of nickel contact allergy at the global level.

In detail, the geographical distribution of nickel awareness is heterogeneous and tends to be higher in Mediterranean countries than in Northern Europe, probably due to a late and less stringent application of the European Directive.

Outside the European Union, specifically in North America and Japan, there continues to be a higher and increasing prevalence of nickel sensitisation over the years, due to the lack of restrictive legislation in this area.

The University of Trieste study points out that the prevalence of nickel sensitisation was 26.1% during the study period (1997-2023), followed a progressively decreasing time trend and was significantly lower in males. The trend also revealed an inverted U-shaped trend with respect to the year of birth among women, falling from 35.70% in those born between 1955 and 1964 to 46.24% in those born between 1965 and 1974, to 41.36% among those born in 1975-1984.

The inverted U-shaped pattern of positive reactions to patch tests by year of birth reflects nickel exposure and sensitisation in women aged 20 to 50 years, prior to the entry into force of the European Directive.

As regards the work performed by the persons surveyed, there was a significantly higher prevalence of positive reactions to the patch test among traders, while it was lower among pensioners and housewives. A higher prevalence of positive reactions among traders could reflect prolonged exposure in professions involving coin manipulation, while age-related immunosenescence could explain the lower prevalence of sensitisation in pensioners and housewives.

Although decreasing over the years, the prevalence of positive reactions to nickel has nevertheless remained higher than that of the northern European countries, probably due to a late and less rigorous application of the aforementioned European Directive. Other factors that may contribute to the higher prevalence of sensitisation in Mediterranean countries than in Northern Europe include social trends that have prompted Italian women to use nickel-containing jewellery products early, and higher ambient temperatures that facilitate the release and penetration of allergens into human skin from nickel-containing products.