D3.252 - Water-induced localized urticaria: A rare case of aquagenic urticaria

Background: Aquagenic urticaria is a rare form of chronic induced urticaria triggered by contact with water, regardless of temperature or salt content. While clinical presentations are often generalized, localized forms are less frequently reported and are usually dependent on water salt content. We report a case of localized aquagenic urticaria affecting the trunk.

Case Presentation: A 28-year-old female with mild persistent allergic rhinitis and childhood-onset asthma reported recurrent pruritic micropapular erythematous lesions on the shoulders, anterior trunk, and dorsal region since the age of 18, triggered by water exposure including bathing, rain, and sweating. Usually, last less than 1 hour but sometimes she takes oral H1 antihistamine (ebastine 10mg). A water provocation testing with tap water-embedded compress on the forearm was negative. Repeat water provocation test with room-temperature tap water compresses applied to the shoulders and upper trunk region for 20 minutes elicited localized pruritus within 5–8 minutes of contact, followed by development of erythematous, small and intensely itchy wheals at the application site 3 minutes after compresses removal, consistent with localized aquagenic urticaria. Lesions resolved spontaneously within one hour. A TempTest® was negative which excludes cold contact urticaria.

Conclusion: This case illustrates a rare presentation of localized aquagenic urticaria, highlighting the importance of targeted provocation testing for accurate diagnosis and to reassure the patient. Clinicians should consider localized variants of chronic inducible urticaria in patients presenting with reproducible lesions restricted to specific body regions.