Aquagenic urticaria still a challenging condition

Skin & Allergy News, Feb, 2003 by Damian McNamara

PRAGUE, CZECH REPUBLIC -- Treatment of aquagenic urticaria--a condition in which some patients react strongly within minutes of exposure to water--remains challenging, according to cases presented at the 11th Congress of the European Academy of Dermatology and Venereology.

The condition is characterized by pinpoint, fleeting, follicular wheals on an erythematous base. The upper parts of the trunk and arms are usually affected, and systemic symptoms are rare.

The pathogenesis remains unclear. Some patients react to all types of water, others do not. Tap water is the most common sensitizer, according to Dr. Rosella Gallo of the department of dermatology, University of Genoa (Italy).

Aquagenic urticaria is relatively rare, with about 40 cases reported in the literature. Some demonstrate a familial link.

A differential diagnosis includes ruling out aquagenic pruritus (characterized by itch without wheeling), cholinergic urticaria, and cold urticaria. In a case presented by Dr. John Carey, dermatology resident at the University of New Mexico Health Sciences Center in Albuquerque, a bag filled with ice water did not elicit an eruption. However, a paper towel moistened with lukewarm water caused a local reaction after 5 minutes in a 38-year-old man; he developed numerous erythematous, urticarial papules.

The man reported that water caused pruritic eruptions after he began taking morphine for chronic headaches. The rash usually resolved after a few hours. Sweating induced a similar eruption in the axillae. The patient was otherwise healthy and took no other medications. He demonstrated sensitivity to water only on days that he took morphine, and he had no further problems following discontinuation.

In some patients, pretreatment with acetone or ethanol enhances the urticant effects of water, Dr. Gallo said. In addition, salinity may be a factor, with hypertonic saline causing a stronger reaction than tap water or regular saline.

Treatment includes reducing contact with water, administering oral antihistamines, and pretreating the skin with petroleum jelly.

Dr. Gallo treated a 36-year-old woman with a 4-year history of urticaria. Her reactions were localized along her face contour and neck. She became increasingly sensitive to water, first reporting a rash after sea bathing, then swimming in a pool, and finally from contact with tap water. Again, water temperature was irrelevant, ruling out urticaria caused by exposure to cold.

The patient was challenged with seawater, ultrafiltered seawater, tap water, distilled water, hypertonic saline, and a glucose solution. "The patient reacted strongly to sea water and hypertonic saline, weakly to tap water, and not to the others," Dr. Gallo said. "We concluded her condition was localized and histamine-related, and influenced by saline concentration and not by osmotic pressure."