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Authors: Claudia Hadlow, Medical Student, University of Notre Dame Australia, Sydney, NSW, Australia; Matthew James Verheyden, Medical Student, University of Notre Dame Australia, Sydney, NSW, Australia; Dr Tevi Wain, Consultant Dermatologist, The Skin Hospital, Westmead, NSW, Australia. DermNet NZ Editor in Chief: Adjunct A/Prof. Amanda Oakley, Dermatologist, Hamilton, New Zealand. Copy edited by Gus Mitchell. November 2019.
Aquagenic urticaria is a rare variant of chronic inducible urticaria induced by contact with water [1,2].
Less than 100 cases of aquagenic urticaria have been reported in the medical literature . There is a higher prevalence among females, with the typical age of onset during or after puberty . Most cases have occurred sporadically, but several familial cases have also been reported .
The exact pathogenesis of aquagenic urticaria is not yet known, but a number of hypotheses have been proposed.
Water reacts with unknown components within the skin, causing histamine release from mast cells and the formation of an urticarial rash. Triggers may include:
Aquagenic urticaria appears whatever the water temperature, saltiness, or pH, and is not dependent on psychogenic factors .
Skin contact with water results in symptoms within 20–30 minutes.
Rarely, the patient may also experience systemic symptoms of wheezing and shortness of breath .
Intense or prolonged itching results in excoriations that can be secondarily infected and start to ulcerate and scar.
Patients with aquagenic urticaria may suffer from psychological stress due to a fear of water.
A clinical history of urticaria in response to water exposure is suspicious of aquagenic urticaria, but the diagnosis should be confirmed by a positive water provocation test and exclusion of other types of chronic inducible urticaria.
A water provocation test can be performed to test for aquagenic urticaria using the following method:
To exclude cholinergic urticaria, examine for urticaria after an exercise test to raise the core body temperature . Other physical urticarias to exclude on testing include pressure urticaria, cold urticaria, and heat urticaria.
Aquagenic urticaria must be distinguished from other forms of inducible urticaria, including :
As it is impossible to avoid water completely, treatment is aimed at preventing or minimising symptoms induced by contact with water.
The main treatment is to take a daily non-sedating, second-generation H1 antihistamine, such as cetirizine, loratadine, or fexofenadine prophylactically .
Other reported treatments include:
The rate of remission of aquagenic urticaria is unknown.
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