Aquagenic urticaria

The symptoms of aquagenic urticaria (inaccurately called water allergy) are similar to all the other types of physical hives. 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.[3] 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. It most commonly develops on the neck, upper trunk and arms, although it can occur anywhere on the body. Once the water source is removed, the rash generally fades within 30 to 60 minutes.[4]

The exact underlying cause of aquagenic urticaria is poorly understood.[5] As of 2016, the main scientific ideas about the cause are that the person is reacting to tiny amounts of an unknown substance dissolved in the water, or that the water interacts with or combines with an unknown substance present in or on the skin, and that the person's immune system is reacting to this compound.[1] Despite the common name water allergy, this condition cannot be a true allergy to water, especially given that the body is largely composed of water.

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 aquagenic urticaria frequently accompanies other types of physical urticaria, the doctor may perform tests to check for these other conditions. An ice cube may be placed on the forearm for a few minutes to check for cold urticaria, exposure to a hot bath will be used to check for Cholinergic urticaria and the lesions will be inspected to determine the root cause of their appearance.[6]

Evaluations for aquagenic urticaria consist of a clinical history and water challenge test.[7] The standard test for aquagenic urticaria is application of a 35 °C water compress to the upper body for 30 minutes. Water of any temperature can provoke aquagenic urticaria; however, keeping the compress at a similar temperature to that of the human body (37 °C) 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 urticaria. Aquagenic urticaria should be distinguished from aquagenic pruritus, in which brief contact with water evokes intense itching without wheals or erythema.[8] The pathogenesis of aquagenic urticaria is not fully known; however, several mechanisms have been proposed.[9] 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 release of histamine.[10]

Aquagenic urticaria, once known as a rare physical urticaria, is reclassified as separate subtype of urticaria.[11] It was first reported by Walter B Shelley et al. in 1964.[12] Itchy hives on contact with water mostly presenting for the first time during puberty in females. Males are less often affected.[13][14][15] Even if majority cases are sporadic in nature, familial cases are also recorded.[16][17][10] Water in all forms such as tap or sea water, swimming pool water, sweat, tears and saliva can induce the lesions.[18][19][20]

There is a lack of desensitization for water and aqua intile injection as allergen even on repeated exposure.[21] 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.[22] Oil in water emulsion creams, or petrolatum as barrier agents for water can be used prior to a shower or bath with good control of symptoms.[23] Therapeutic effectiveness of various classes of drugs differ from case to case.

There is no treatment that will permanently rid the person of symptoms of aquagenic urticaria, but healthcare providers can prescribe a medication to calm the hives/ breakout. Most treatments are used to lessen the effects of the disease to promote more comfort when the body must come in contact with water.[6]

• Oral antihistamine[1]
• Topical corticosteroids: specifically stanozolol.[1]
• Phototherapy[1]
• Barrier cream:[1] In some circumstances an oil in water solution or emulsion cream can be applied to the skin to protect it from water exposure while washing or performing aquatic activities.

• Aquagenic pruritus
• Aquadynia
• Cholinergic urticaria
• Solar urticaria
• List of cutaneous conditions