Contact Stomatitis Toothpaste — ORE Part 1 MCQ
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Correct answer: E — Allergic contact reaction to cinnamonaldehyde
The best answer is E. Cinnamon flavouring, particularly cinnamonaldehyde, is a recognised toothpaste contact allergen. The onset after repeated exposure to a new product, together with erythema and superficial sloughing, is most consistent with allergic contact stomatitis, a delayed (type IV) hypersensitivity reaction. In a UK case series, patch testing implicated cinnamonaldehyde; improvement followed toothpaste avoidance and symptoms commonly recurred on rechallenge. Immediate allergy would be expected to occur rapidly and may include urticaria, angioedema or systemic features. An autoimmune disorder would not be explained by a discrete toothpaste exposure. Fluoride toxicity is not the expected presentation with ordinary toothpaste use. Detergents such as sodium lauryl sulphate can cause irritant reactions, but the cinnamon-specific exposure makes allergic contact stomatitis the more defensible diagnosis.
Reference: Lamey PJ, Lewis MA, Rees TD, et al. Sensitivity reaction to the cinnamonaldehyde component of toothpaste. British Dental Journal. 1990;168(3):115-118. https://pubmed.ncbi.nlm.nih.gov/2306395/