What Is Aquagenic Pruritus?

Overview

Water is a vital substance for all living organisms. It keeps us hydrated, regulates body temperature, and maintains healthy skin and digestion. However, despite its ubiquitous presence, water can pose an unexpected challenge for some people. Aquagenic Pruritus (AP) is a rare medical condition that causes severe skin itching accompanied by prickling, tingling, or burning-like sensation. The term Aquagenic Pruritus means ‘Water-induced pruritus’. AP has become a  global dermatological problem.¹ This condition is caused by skin contact with water.² Various attributes of water influence skin itching in people affected by AP, such as its temperature, chemical composition, PH level, and cleansing agents used for cleaning or bathing.³

AP was first described by Shelly in 1970 in the Journal of the American Medical Association and compared with Aquagenic Urticaria (AU) by Greaves in 1981.⁴ Unlike AP, AU appears as hives (skin rash) when skin is exposed to water, regardless of its temperature. It causes generalised skin rash and itching that occurs on the chest, neck, and arms.⁵ However, AU develops within 20 to 30 minutes of contact with water, and remission happens after 30 to 120 minutes.⁶ 

AP can be hereditary, in which one-third of patients have a family history of the condition. Meanwhile, the other form of AP appears specifically in the elderly population (above 60 years) as they are more susceptible to dry skin.² Generally, AP affects both males and females equally. The mean age of presentation is 25 ± 3.8 years. It peaks during infancy, adolescence or early childhood. This distressing condition becomes burdensome because it fosters a fear or phobia of water, which significantly disrupts the daily lives of those affected.^2,3

Causes of aquagenic pruritus

AP is characterised by its idiopathic nature (nonapparent cause), exclusively triggered by contact with water. The mechanism of AP occurrence is still under investigation; however, the most accepted explanation is the increased mast cell degranulation and subsequent release of histamine, which plays a key role in causing pruritus (itching).

Moreover, AP is linked to several biochemical reactions in the body, such as the release of acetylcholine and neuropeptides, increased cutaneous fibrinolytic activity, and the simulation of a dysfunctional sympathetic nervous system.¹ Additionally, AP can occur as a symptom of other conditions, including:³

• Hypereosinophilic Syndrome, increase in eosinophils (white blood cells) causing organ damage
• Juvenile Xanthogranuloma, excess histiocytes that cause skin lumps
• Polycythemia Vera (PV), a type of blood cancer in which the bone marrow makes too many red blood cells. PV causes generalised itching triggered by water contact, especially during hot showers, sudden temperature changes, or exercise-induced sweating. Around 50% of PV cases are preceded by AP, prompting a physician to consider a haematological condition as a potential underlying cause when AP is present^2,4
• Leukocytoclastic Vasculitis, small blood vessel inflammation that causes hypersensitivity⁷
• Lymphoblastic Leukemia, a type of blood and bone marrow cancer
• T-Cell Non-Hodgkin’s Lymphoma, a type of cancer that affects the lymphatic system
• Metastatic Squamous Cell Carcinoma, a type of cancer that begins as a growth of cells on the skin
• Hepatitis C, a liver inflammation caused by virus infection
• Lactose Intolerance¹
• Antidepressant medications like Bupropion and Clomipramine and antimalarial drugs such as Hydroxychloroquine and Chloroquine can cause AP

Signs and symptoms of aquagenic pruritus

Symptoms like generalised itching, tingling, stinging, and burning sensation occur after immediate contact with water. These symptoms may last up to 2 hours; however, they disappear within an hour in most cases. AP is not associated with skin rash or wheals because of the slow and constant release of histamine in the skin. Other stimuli that can trigger the symptoms include perspiration (sweating), ambulating in and out of bed, alteration in the surrounding environment, hot and cold temperatures, physical exertion, emotional and mood changes, and pressure.⁸ According to previous studies, cold water and sweating exacerbate AP symptoms, while hot water improves the symptoms.

The commonly affected areas by AP are the face, feet, hands, upper arms (dorsal and ventral sides), and the front of thighs and legs.⁴ In rare cases, AP may extend to the soles, palms, and mucosal areas of the body.¹ 

Complications of aquagenic pruritus

AP causes intense itching that interferes with daily activities. It can also cause Lichen simplex, Prurigo nodules, wearing of skin, sleep disturbance, psychological disturbance, and avoid bathing.² 

Management and treatment of aquagenic pruritus

There is no cure for AP; however, various treatments are available to help control the condition. These treatments include:

• Capsaicin cream on the affected area
• Bathing with baking soda to raise the water pH and reduce pruritus
• Baby oil before or after a shower
• Lanolin-free aqueous cream and emollients after a shower
• Hydroxyzine and petrolatum ointment work as barrier creams that prevent water-induced pruritus 
• Ultraviolet-B Phototherapy in a clinical setting
• Antihistamines such as Claritin and Cimetidine and Analgesics 
• Selective serotonin reuptake inhibitors (SSRIs)
• Transcutaneous Electrical Nerve Stimulation (TENS), is a procedure used to reduce pain
• PV associated with AP can be treated with Photochemotherapy (PUVA) and Janus kinase (JAK) 1/2 inhibitors² 

Moreover, some strategies can help to reduce the intensity of itching, such as: 

• Use of cotton clothing and bedding
• Increasing shower water temperature for the last five minutes
• Using heat pads or hair dryer after shower

However, these strategies might not work for some patients or might induce more itching. 

Diagnosis of aquagenic pruritus

AP is diagnosed based on the symptoms. The doctor will ask about your family history and perform a physical examination. In addition, the doctor will try to exclude other medical conditions that cause generalised itching without an observable skin lesion.

The following criteria should be considered when diagnosing AP: 

• Water contact causes intense and severe itching, prickling, stinging, or burning-like sensation irrespective of water type and properties
• Symptoms develop within minutes after water contact
• No observable skin changes
• No underlying medical condition or coexisting skin condition that explain the discomfort
• Exclusion of urticaria, symptomatic dermographism, and PV⁸ 

Differential diagnosis

Distinguishing AP from other skin conditions, especially PV, is crucial. Some of the differentiating factors include:⁸ 

• Xerosis or Eczema – Rough and dry skin with scaling
• Aquagenic Urticaria – Hives occurring due to exposure to water
• Cholinergic Urticaria – Hives occurring due to an increase in body temperature and sweating⁹
• Cold Urticaria – Hives occurring from exposure to cold
• Heat Urticaria – Hives triggered by heat or physical stimuli
• Vibratory Urticaria – Skin reaction to vibration

FAQ

Can aquagenic pruritus be prevented?

The exact cause of AP is unknown, and currently, there are no available preventive measures. However, controlling symptoms can include following strategies like using cotton clothing and bedding, applying capsaicin cream, and taking baking soda baths to help reduce symptoms.

Is there a cure for aquagenic pruritus?

There is no cure for AP, and it could be an initial symptom of PV or other conditions. AP precedes PV by around five years; thus, a doctor may recommend a blood test to exclude the possibility of PV and ascertain the diagnosis.

How common is aquagenic pruritus?

AP is a rare condition that affects both males and females; however, AP in the elderly shows a higher occurrence among women above 60 compared to men. Its prevalence is unknown, and it is not commonly diagnosed due to its potential association with psychiatric-like conditions.

When should I see a doctor?

If you are experiencing intense itching, tingling, or burning sensation immediately after water contact, then it's recommended to consult a doctor to determine the cause of these symptoms. Early diagnosis of AP provides relief to patients, sparing them from assuming it was a psychological issue.¹

Summary

• Aquagenic Pruritus (AP) is a rare skin condition causing generalised itching, pickling, tingling, and burning sensation upon water contact, regardless of temperature or other factors
• Its cause remains unknown, yet it's linked to increased mast cell degranulation and histamine release. It can also signal underlying systemic conditions like Polycythemia Vera (PV) and other diseases such as leukaemia or vasculitis
• While there is no cure, managing AP involves various treatments like antihistamines, phototherapy, emollient and barrier creams, and lifestyle adjustments to reduce skin discomfort
• Consulting a medical professional is crucial to determining the underlying cause