Cosmetovigilance for infrequent allergens in Spain using a national online registry: The example of allergic contact dermatitis caused by phenylethyl resorcinol.

BACKGROUND: Monitoring of adverse events induced by cosmetics performed by health authorities, known as cosmetovigilance, has been relied on the collection of case notifications. OBJECTIVES: We aimed to show how a contact dermatitis registry can contribute to the cosmetovigilance of emerging allergens. We used the example of phenylethyl resorcinol, an infrequent allergen with only 6 previous cases reported in Europe and Japan since 2013. METHODS: A systematic search in the Spanish Registry of Contact Dermatitis and Cutaneous Allergy (REIDAC) database was performed to identify patients with positive patch test to phenylethyl resorcinol or cosmetics that contains it between June 2018 and January 2023. We collected the main clinical features of these patients and compared them with those of patients recorded in the registry with similar epidemiological features. RESULTS: Thirteen patients with positive patch test to phenylethyl resorcinol were identified. All the patients were women with a mean age of 42 years (range 32-59) and their lesions were mainly in the face. CONCLUSION: Assessing the importance of infrequent allergens based solely on a case series is difficult. Multicentre registries facilitate the collection of cases and provide appropriate background information for new allergens.