Is a Life Without Water Possible? Aquagenic Urticaria: Report of a Case and Review of the Literature

Introduction

Aquagenic urticaria (AU) is an uncommon form of physical urticaria triggered by water exposure. First described by Shelley and Rawnsley in 1964, fewer than 100 cases have been documented.^1,2 After water contact, regardless of temperature, patients develop pruritic, small, punctate (1–3 mm) wheals surrounded by erythema (1–3 cm) within 20–30 min. These lesions typically resolve within 30–60 min after cessation of contact.^1,3AU most commonly affects the trunk and upper extremities, with palms and soles generally spared. The wet towel provocation test, involving the application of a compress soaked in 35°C–37°C water or physiological saline, is the diagnostic standard. A positive result is indicated by the development of urticarial lesions within 40 min of the application or 10 min after removal. ⁴ Here, we present the clinical and laboratory findings, along with management details, of a 12-year-old female diagnosed with AU, supported by relevant literature.

Case Presentation

A 12-year-old female patient presented with a 3-month history of pruritic erythema and wheals on skin areas exposed to water, appearing 5–10 min after swimming in the sea or showering. Symptoms lasted 30–60 min and resolved spontaneously. Photographic evidence of previous episodes revealed small urticarial lesions. The lesions were confined to the neck, back, and chest, sparing the palms, face, and legs. No additional triggers, such as specific foods, medications, stress, or exercise, were identified, and the rash was not associated with systemic symptoms such as cough, wheezing, abdominal pain, vomiting, or hypotension.

The patient’s medical history was unremarkable for chronic diseases, regular medications, or supplements. No additional allergic symptoms were reported, and her family history was negative.

Physical examination, including skin and systemic evaluations, showed no significant findings, with no dermatographism observed.

Laboratory tests revealed a normal complete blood count, a peripheral eosinophil count of 100/mm³, an erythrocyte sedimentation rate of 2 mm/h, and a serum total IgE level of 12.4 IU/mL. Specific IgE tests for aeroallergens, including grass mix, dust mix, olive tree, Aspergillus fumigatus, and cat dander, were negative. Thyroid hormone levels, C-reactive protein, and routine biochemical tests were within normal limits. An anti-thyroperoxidase antibody, anti-thyroglobulin antibody, and antinuclear antibody tests were negative. Urinalysis results were unremarkable, and viral screening tests (hepatitis B, hepatitis C, and HIV) were negative. The patient’s urticaria control test (UCT) score was 6, indicating poor control.

The patient, who specifically reported rashes following exposure to seawater or showering but did not experience symptoms when washing her hands or face, underwent an ice cube test to rule out cold urticaria. The test yielded negative results. Subsequently, a water provocation test was performed using a towel soaked in 35°C tap water, which was applied to the patient’s back, given the preliminary diagnosis of AU. This test was conducted during the summer. To ensure reliable results, the towel was replaced with a freshly soaked one at the 10th min. Within 20 min, the patient reported itching, and urticarial lesions appeared at the test site. Consequently, AU was confirmed through the wet towel provocation test (Fig. 1A, B, C).

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FIG. 1.

Figure 1 demonstrates the wet towel provocation test and patient results. Image (A) shows the application site of the wet towel soaked with 35°C water to the child’s back; (B) shows the urticarial lesions that developed at the test site 20 min following the application of the wet towel; (C) highlights these lesions.

The patient was prescribed 20 mg of the second-generation antihistamine bilastine, to be taken once daily with additional doses as needed. She was also advised to apply liquid petroleum jelly as a topical barrier cream before water exposure. Bath durations were restricted to minimize symptoms.

Although systemic symptoms have not been reported to date, the patient was prescribed an epinephrine auto-injector and received training on its proper use to manage potential systemic reactions.

After 1 month of antihistamine therapy and preventive measures, the patient’s symptoms improved. Her follow-up UCT score was recorded as 11. However, her lesions worsened with excessive sweating or prolonged water exposure. The family was informed that the antihistamine dose could be increased by two- to fourfold if necessary and that omalizumab could be considered as an alternative treatment despite the patient’s low IgE levels. At present, the patient is on twice-daily antihistamine therapy at the family’s request.

Discussion

AU is a rare type of physical urticaria triggered by water exposure. It is slightly more common in females than males, with most cases presenting during or after puberty. ⁵ In our female patient, the symptoms also began during puberty, aligning with the existing literature.

Although most AU cases are sporadic, familial occurrences have been documented.^2,6 For instance, AU observed across three generations of a family has been associated with lactose intolerance due to lactase enzyme deficiency encoded on chromosome 2. However, this genetic link remains inconclusive and may be coincidental. ⁶ No similar complaints were reported in our patient’s family.

In AU, lesions typically develop independently of water temperature and pH, as observed in our patient. ⁷ Reactions to saltwater are variable. Tkach ⁸ reported a case of urticaria triggered by tap water, snow, and sweat but not seawater, hypothesizing that sudden osmotic pressure changes around hair follicles may contribute to lesion development. Other studies suggest that increased salt concentration and water osmolarity may enhance the solubility and penetration of triggering epidermal antigens.^9–11 Body fluids such as sweat and tears have also been reported to trigger urticaria. ² Our patient initially tolerated brief water exposure and reported lesions only after contact with seawater and tap water. However, over time, she began experiencing reactions to sweat as well. Notably, the severity of the rash was greater with seawater exposure than with tap water.

The pathogenesis of AU remains poorly understood. Early literature suggested that a toxic substance formed by the interaction of water and sebum could cause mast cell degranulation. ¹ Czarnetzki et al. ¹² hypothesized that a water-soluble antigen located in the epidermis diffuses into the dermis upon contact with water, triggering histamine release from mast cells. While cholinergic pathway activation has been implicated in AU, evidence remains inconsistent. For example, scopolamine, an acetylcholine antagonist, has been reported to prevent lesions in some cases, whereas atropine, a similar agent, has shown no such effect.^12,13

For patients with a typical clinical history, the wet towel test offers a simple, cost-effective diagnostic method and can minimize the need for advanced investigations. In the differential diagnosis of AU, conditions such as aquagenic pruritus, cholinergic urticaria, cold urticaria, and other chronic urticarias should be excluded. Complementary physical urticaria tests may be necessary.^3,4 In our case, AU was diagnosed using the wet towel test, while cold urticaria was ruled out through the ice cube test.

Although our patient did not exhibit systemic symptoms, systemic manifestations of AU have been reported in the literature.^2,5 AU may also present as a manifestation of systemic diseases or in association with malignancies.^14–16 In our patient, who had experienced dermatological symptoms for 3 months without evidence of an underlying systemic condition, we opted for regular follow-up, symptom monitoring, and repeat laboratory evaluations as clinically indicated.

The UCT is a validated tool for assessing disease control in chronic urticaria, including chronic spontaneous and chronic inducible forms. ¹⁷ We utilized the UCT in our patient’s clinical follow-up.

First-line treatment for AU includes antihistamines, followed by topical barrier creams, phototherapy, and omalizumab.^2,3,18,19 Stanozolol, a synthetic anabolic-androgenic steroid, has also shown efficacy in AU patients with comorbid conditions such as HIV and hepatitis C. ¹⁵ In our patient, partial symptom control was achieved by doubling the antihistamine dose. Although her total IgE level was below 30 IU/mL, omalizumab is planned for initiation during follow-up upon obtaining family consent, as certain urticaria cases benefit from omalizumab despite low IgE levels.

Because avoiding water as a trigger is nearly impossible, AU significantly affects patients’ quality of life. Conservative approaches, such as applying barrier creams before water exposure and limiting bath durations, are essential. Symptomatic treatments similar to those used for other chronic urticarias are also recommended. In addition, patients should receive detailed guidance on the use of adrenaline auto-injectors to manage potential systemic reactions, such as anaphylaxis. Close monitoring throughout the disease course is crucial for effective management and safety. Further research is needed to clarify the pathogenesis, comorbidities, and specific treatment strategies for AU.

Ethical Approval and Trial Registration

The case description was performed in accordance with the ethical standards outlined in the Declaration of Helsinki and its latest amendments.

Consent for Publication

Written informed consent was obtained from the parents for the publication of the case report and photographic images.