TOPLINE

In two retrospective cohorts from Belgium and Netherlands, tin allergy was more common than previously reported, with positivity rates up to 11.4% and about 27%-32% of patients with positive patch test results having clinically relevant reactions. Symptoms in or around the mouth were the most frequent presentation, and tin-containing toothpaste was the leading identified source of exposure.

METHODOLOGY

• Researchers analyzed retrospective data from two independent cohorts, one in Antwerp and one in Amsterdam, to estimate how often tin sensitization occurred and how often it was clinically relevant.
• The Antwerp cohort included 1919 patients who underwent routine patch testing. The Amsterdam cohort included 536 patients (median age, 57 years; 74.8% women) referred for suspected metal allergy or mouth-related complaints.
• Patients in the Antwerp cohort were tested with metallic tin, tin oxalate, and/or tin chloride, whereas patients in the Amsterdam cohort were tested with tin chloride only.
• In Antwerp, clinical relevance required plausible tin exposure and symptoms whose timing, location, and appearance were consistent with tin exposure. In Amsterdam, it required confirmed exposure and symptoms that could be explained by the exposure, such as reduction in symptoms after stopping tin-containing products.
• Patients in the Amsterdam cohort with positive test results also completed a standardized questionnaire on exposure to tin fluoride-containing oral products, canned foods, and dental alloys.

TAKEAWAY

• In the Antwerp cohort, 128 patients (6.7%) had positive reactions to one or more tin preparations; 35 of them (27.3%) had clinically relevant sensitization.
• In the Amsterdam cohort, 61 patients (11.4%) tested positive for tin chloride; among the 50 patients in whom clinical relevance was assessed, 16 (32%) had clinically relevant sensitization.
• Toothpaste was the most common suspected source among patients with clinically relevant sensitization, identified in 27 of 35 patients (77.1%) in the Antwerp cohort and 10 of 16 patients (62.5%) in the Amsterdam cohort. The remaining six patients in the Amsterdam cohort were exposed to tin-containing dental materials.
• Among the patients in the Antwerp cohort with clinically relevant sensitization, symptoms most often involved the mouth and surrounding skin (19 of 35 patients; 54.3%), followed by the skin around the eyes (10 of 35 patients; 28.6%). In 10 patients, makeup, mainly eye shadow listing tin oxide, was the most likely source of exposure.

IN PRACTICE

"Taken together, our retrospective findings appear to support tin as a relevant and potentially emerging allergen and raise the question of why the observed prevalence of sensitization appears higher than previously reported," the authors wrote.

"It is likely that, currently, patients with potentially relevant tin sensitization may be overlooked in daily clinical practice as this particular metal, to our knowledge, is currently not a routinely tested allergen in consecutive patients in most centres," they added.

SOURCE

Sylvie M. Franken, with the Amsterdam University Medical Center, Amsterdam, Netherlands, was the corresponding author of the study, which was published online on September 23 in Contact Dermatitis.

LIMITATIONS

Differences in patient selection, test materials, and assessment of clinical relevance meant the two cohorts could not be directly compared. In the Antwerp cohort, not all patients received the same tin tests, and some weak reactions to tin chloride may have been irritant reactions rather than allergic reactions. Cosmetic products were not patch tested; therefore, tin oxide was identified as the likely source based only on ingredient labels, and other ingredients could not be ruled out.

DISCLOSURES

The authors reported no funding for the study. One author disclosed serving as a consultant, investigator, and/or speaker for several pharmaceutical and cosmetic companies.

This article was created using several editorial tools, including AI, as part of the process. Human editors reviewed this content before publication.