Nickel is the Most Prevalent Allergen in Pediatric Patients With and Without Atopic Dermatitis

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Through a systemic review, investigators analyzed the worldwide prevalence of contact allergy and triggering allergens in pediatric patients between 2010 and 2024.¹ It was found that nickel was the most common allergen in all children, including those with atopic dermatitis (AD). Additionally, higher allergen rates were found in the United States, when compared to other geographical regions like Europe.

A literature search was conducted on PubMed, Embase, and Web of Science, including all articles published between January 2010 and May 2024. Eligible studies had to include ≥ 100 patch-tested patients under the age of 18, analyzing the number of patients with AD and the number of those without.

The initial search yielded 23,191 results. However, only 17 studies were included in the final analysis. They involved a total of 11,593 patients with 4176 positive patch tests. Over 57% were female and the mean age was 11.3 years.

Of these studies, 12 reported the number of patients with AD and thus observed 1,955 positive patch tests in these cases. A total of 52 allergens were reported. Studies were conducted in the United States, Italy, Sweden, Israel, Denmark, Czech Republic, Turkey, Thailand, India, The Netherlands, and Belgium, with a generally low risk of bias.

Out of the tested metals, nickel sulfate had the highest prevalence and proportion of positive patch tests in all children at 11.9% (95% CI, 8.6%–15.71%). This was demonstrated in 16 of the studies.

“The prominence of nickel as the leading allergen with the highest proportion of positive patch tests aligns with existing literature, highlighting its ubiquitous presence in various consumer products including jewelry, clothing fasteners, and household items,” the authors wrote.

Cobalt had a pooled proportion of 6.6% (95% CI, 4.2%–9.5%), which was observed in 14 studies. On the lower end, potassium dichromate was 4.2% (95% CI, 2.1%–7.0%) and gold was 3.9% (95% CI, 0.01%–14.1%).

Perfume allergens were also tested. Fragrance mix I had a rate of 4.8% (95% CI, 2.9%–7.1%) while fragrance mix II had a lower rate of 3.0% (95% CI, 2.3%–3.7%). Results were also analyzed for hydroxyisohexyl 3-cyclohexene carboxaldehyde (0.5%. 95% CI, 0.2%–1.0%) and Balsam of Peru (3.1%, 95% CI, 1.5%–5.3%).

Nickel also showed the highest proportion of positive patch tests in children with AD, with a pooled prevalence of 12.6% (95% CI, 7.8%–18.4%). Besides nickel, cocamidopropyl betaine (9.0%, 95% CI, 7.3%–10.8%), cobalt (8.2%, 95% CI, 4.8%–12.5%), and fragrance mix I (6.6%, 95% CI, 4.8%–12.5%) had the highest rates, similar to what was noted in the main analysis.

Compared to all patients, children with AD had a significantly higher proportion for cocamidopropyl betaine (9.0% vs. 5.5%, p = 0.0030), propylene glycol (6.6% vs. 3.2%, p = 0.0006), lanolin alcohol (4.2% vs. 2.3%, p = 0.019) and carba mix (3.5% vs. 1.9%, p = 0.023). Conversely, all children had a greater proportion for thiuram mix (2.8% vs. 0.8%, p = 0.0005) and propolis (4.3% vs. 2.6%, p = 0.039).

More of these high allergen prevalences were found in the United States, compared to other geographical regions like Europe, indicating the potential need for more standardized regulations. A baseline series for pediatric patch testing is currently being developed by the European Society of Contact Dermatitis.² With this initial finding, further region-specific research is recommended.

“The geographical variations are a multifaceted phenomenon influenced by multiple factors including environmental, cultural, and regulatory factors,” the authors wrote. “Comparing Europe to the United States, notable differences should be considered regarding tightened regulatory measures in Europe compared to the United States.”

References

1. Isufi D, Jensen MB, Kursawe Larsen C, Alinaghi F, Schwensen JFB, Johansen JD. Allergens Responsible for Contact Allergy in Children From 2010 to 2024: A Systematic Review and Meta-Analysis. Contact Dermatitis. Published online January 19, 2025. doi:10.1111/cod.14753

2. Cafone J, Ruffner MA, Spergel JM. The Role of Eosinophils in Immunotherapy. Curr Allergy Asthma Rep. 2020;20(1):1. Published 2020 Jan 7. doi:10.1007/s11882-020-0895-x