Specialty dermatology OMIM 191850 | ICD-10 L50.8 (ILDS L50.830) MeSH C562481 | |
Aquagenic urticaria, also known as water allergy and water urticaria, is a diagnosed form of physical urticaria. The defining symptom is a painful skin reaction resulting from contact with water. It is sometimes described as an allergy, although it is not a true histamine-releasing allergic reaction like other forms of urticaria. This seems to not be affected by different temperatures of water, such as cold or hot, or chemicals such as fluorine and chlorine, since it is reproduced with distilled water and medical saline. According to Gerald W. Volcheck, “Urticaria represents transient, localized areas of oedema within skin tissue that appear as pruritic, raised erythematous, skin-colored or white, non-pitting, blanching plaques of variable size”. The term urticaria was first used by the Scottish physician William Cullen in 1769. It originates from the Latin word urtica, meaning stinging hair or nettle, as the classical presentation follows the contact with a perennial flowering plant Urtica dioica. The history of urticaria dates back to 1000–2000 BC with its reference as a wind-type concealed rash in the book The Yellow Emperor's Inner Classic from Huangdi Neijing. Hippocrates in the 4th century first described urticaria as "knidosis" after the Greek word knido for nettle. The discovery of mast cells by Paul Ehrlich in 1879 brought urticaria and similar conditions under a comprehensive idea of allergic conditions.
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Gender and aquagenic urticaria
Aquagenic urticaria, once known as a rare physical urticaria, is reclassified as separate subtype of urticaria. It was first reported by Walter B Shelley et al in 1964. Pruritic hives on contact with water mostly presenting for the first time during puberty in females of reproductive age is seen in aquagenic urticaria. Males are less often affected. Even if majority cases are sporadic in nature, familial cases are also recorded. Water in all forms such as tap or sea water, swimming pool, sweat, tears, saliva can induce the lesions.
Symptoms
The symptoms of aquagenic urticaria or water allergy (being allergic to water) are similar to all the other types of physical hives that are caused by various things. This may include wheals or small raised hives, intense itching, skin flushing in the areas that are prone to water contact. The symptoms may appear within minutes after the body comes in contact with the water. Aquagenic urticaria is a rare condition in which itchy urticaria (hives) develop rapidly after the skin comes in contact with water, regardless of its temperature. The hives associated with aquagenic urticaria are typically small (approximately 1–3 mm), red- or skin-colored welts (called wheals) with clearly defined edges. The rash most commonly develops on the neck, upper trunk and arms, although it can occur anywhere on the body. Some people have itching too. Once the water source is removed, the rash generally fades within 30 to 60 minutes.
Prevention
The more poignant part of this disorder is the lack of desensitization for water and aqua intile injection as allergen even on repeated exposure. Avoidance of allergen as a general principle in any allergic disorder necessitates the evasion of water exposure. Topical application of antihistamines like 1% diphenhydramine before water exposure is reported to reduce the hives. Oil in water emulsion creams, petrolatum as barrier agents for water can be used prior to shower or bath with good control of symptoms. Therapeutic effectiveness of various classes of drugs differs from case to case.
Diagnosis
Diagnosis of aquagenic urticaria will begin with an evaluation of the patient's clinical history looking for any signs of what might be causing this severe reaction. The patient will then be put to a water treatment test where water will be applied to the upper body for 30 minutes. Water may be placed directly on the skin or a soaked paper towel may be applied. In many cases distilled water, tap water and saline will be used to check for a difference in reaction. After this is removed the skin will be checked for a reaction for the next 10–15 minutes. Because aqugenic urticaria frequently accompanies other types of physical urticaraia, the doctor may perform tests to check for these other conditions. In ice cube may be placed on the forearm for a few minutes to check for cold urticarial, exposure to a hot bath will be used to check for Cholinergis uticaria and the lesions will be inspected to determine the root cause of their appearance.
Evaluations for aquagenic urticaria consist of a clinical history and water challenge test. The standard test for aquagenic urticaria is application of a 35oC water compress to the upper body for 30 minutes. Water of any temperature can provoke aquagenic urticaria; however, keeping the compress at room temperature avoids confusion with cold-induced or local heat urticaria. In addition, a forearm or hand can be immersed in water of varying temperatures. A diagnosis of aquagenic urticaria requires exclusion of other types of physical urticaria, so an exercise test and ice cube test should be performed to rule out other types of physical urticarial. aquagenic urticaria should be distinguished from aquagenic pruritus, in which brief contact with water evokes intense itching without wheals or erythema. The pathogenesis of aquagenic urticaria is not fully known; however, several mechanisms have been proposed. Interaction with water with a component in or on the stratum corneum or sebum, generating a toxic compound, has been suggested. Absorption of this substance would exert an effect of perifollicular mast cell degranulation with releas of histamine.
Treatment
There is no treatment that will rid the patient of symptoms of aquagenic urticaria. Most treatments are used to lessen the effects of the disease to promote more comfort when the body must come in contact with water.