CD05 Sensitivity to antisensitivity: a case series of stannous salt allergy

Abstract

Toothpaste allergy is an uncommon but recognized cause of cheilitis and stomatitis. While flavourings are frequent culprits, reactions to active agents like stannous (tin) salts, which are increasingly used for dentine hypersensitivity, are likely under-­reported. Diagnosis is complicated by the lack of commercial patch test preparations for stannous fluoride and the irritant nature of toothpaste testing. We aimed to evaluate stannous chloride as a toothpaste allergen. We report nine patients presenting to OneWelbeck Skin Health and Allergy over 12 months (November 2024 to November 2025) with suspected perioral or oral allergic contact dermatitis, in whom patch testing demonstrated reactivity to stannous chloride. Patch testing was performed using the British Society for Cutaneous Allergy baseline series and a dedicated lip series. Tin(Ii) oxalate was used as a confirmatory marker in selected cases to exclude irritancy. Nine patients (seven female, two male; aged 18–62 years) were identified. Presentations included cheilitis (most common), lip swelling and aphthous ulcers. All patients reacted to stannous chloride 1% in petrolatum. Tin(Ii) oxalate (1% in petrolatum) was positive in four of six tested cases, supporting the interpretation of an allergic response. One patient underwent a positive repeat open application test to their stannous-containing toothpaste. Stannous salts are an emerging cause of allergic contact cheilitis. Our findings suggest stannous chloride 1% in petrolatum is a reliable, commercially available marker for diagnosing allergy to stannous-containing oral hygiene products. We recommend including stannous chloride and, where possible, tin(Ii) oxalate in patch test series for patients with recalcitrant oral or perioral dermatitis, particularly when ­stannous-containing products are used. This avoids the challenges of testing irritant toothpaste formulations directly.