A Canadian teenager’s chronic hives, which flared up every time her skin came into contact with water, were finally diagnosed as aquagenic urticaria – an exceedingly rare allergy to water itself. The case highlights the difficulties in identifying unusual allergic reactions and the importance of detailed patient history in diagnosis.
Initial Symptoms and Diagnostic Challenges
The patient first experienced hives around the time she began menstruating two years prior. Regardless of water temperature or source (showers, pools, rain), welts and red patches (1-3 cm wide) would appear within 20 minutes, fading after 30-60 minutes without treatment. Notably, sweat or tears did not trigger the reaction.
This posed a challenge because hives are commonly caused by contact or ingested allergens. The usual immune response – histamine release following exposure – didn’t neatly explain why water alone would cause a reaction. Standard allergy tests for dust, cats, and rabbits came back negative for overlap with the water-induced hives. The patient also exhibited no other allergy symptoms like dizziness or breathing difficulties.
Confirmed Diagnosis Through Provocation Testing
After a failed attempt with antihistamines, doctors performed a provocation test. Exposing the patient’s skin to water under controlled conditions confirmed the reaction: welts appeared within 20 minutes, solidifying the diagnosis of aquagenic urticaria.
This condition is exceptionally uncommon; only around 100 cases have been documented. The underlying cause remains unknown, though it often emerges during puberty and appears more frequently in women. This makes pinpointing the trigger difficult because hives can be induced by pressure, temperature, exercise, or more typical allergens.
Treatment and Long-Term Management
Initial treatment with montelukast (an asthma medication) offered moderate relief but didn’t resolve the issue. The patient responded well to daily cetirizine, an antihistamine targeting allergy symptoms. After eight months, symptoms only returned when she missed doses.
By the 14-month follow-up, the teen reported no restrictions in daily activities and a stable quality of life as long as she continued taking cetirizine. This demonstrates that while rare, aquagenic urticaria can be managed effectively with the right medication.
The case underscores how crucial detailed patient history and direct exposure tests are when dealing with atypical allergic reactions. What appears as a straightforward allergy can sometimes point to conditions that are nearly unique in medical literature.
