The exact reason is not fully understood. But several factors are thought to play a role:

• Too many blood cells: In PV, the excess blood cells may release substances that make skin nerve endings more sensitive [1].
• Histamine release: Histamine is a natural chemical that plays a role in allergic reactions. High levels may trigger itching in PV.
• Water as a trigger: Warm water may increase blood flow to the skin, releasing chemicals that cause rashes or itching.
• Genetic changes in blood cells: Because PV is a blood cancer (a myeloproliferative neoplasm), its genetic changes (like JAK2 mutations) may influence how the body reacts to stimuli [3].

Not all patients experience the same type of rash. Common patterns include:

• Red patches or blotches on the arms, chest, or back
• Raised bumps or hives after bathing
• No visible rash, but intense itching that feels like stinging or burning

A large study found that itching was reported by ~41% of patients with PV, and it significantly lowered their quality of life [2]. Some patients describe it as the single most challenging part of living with PV.

Patients often notice that the rash or itching is worse:

• After a hot shower or bath
• After swimming in pools or natural water
• In warm or humid weather

Even though a rash may not be dangerous by itself, it can cause severe distress and impact daily activities:

• Sleep problems: Itching keeps many patients awake.
• Emotional impact: Constant itching can make people feel anxious or frustrated.
• Social discomfort: Visible rashes or scratching in public can be embarrassing.

In one survey of 441 patients with PV, itching was associated with a significant decrease in quality of life [3].

Lifestyle steps

• Use lukewarm water instead of hot showers.
• Apply fragrance-free moisturizers to keep the skin hydrated.
• Avoid scratching, which can worsen irritation. Try patting or applying a cold compress instead.
• Wear loose, cotton clothing to prevent skin friction.

Medicines that may help

Doctors may prescribe [4]:

• Antihistamines (drugs that block histamine, often used for allergies).
• SSRIs (antidepressants that can reduce itching signals in the brain).
• Phototherapy (controlled light therapy for the skin).

Disease-directed treatments

Some PV treatments not only control blood counts but also help with rash and itching:

• Interferon: shown to improve itching while controlling PV [3].

JAK inhibitors: target the JAK2 pathway and often reduce severe itching [4]

1. Is a rash common in polycythemia vera?

Yes, approximately 4 in 10 to 5 in 10 patients with PV (~40–50%) report itching or rash, especially after contact with warm water [2].

2. Why does water make my rash worse?

Warm water can induce chemicals release like histamine in the skin, which trigger itching in PV. This condition is known as aquagenic pruritus [1].

3. Can the rash be treated?

Yes, options include antihistamines, antidepressants (SSRIs), phototherapy, and PV-directed drugs such as interferon or JAK inhibitors [3][4].

4. Does everyone with PV get a rash?

No, not every patient experiences skin problems, but approximately 41% report itching or rash [2].

5. Should I tell my doctor about PV-related rash?

Yes, even if it seems “minor,” PV rash can lower your quality of life. Your doctor can recommend treatments to alleviate itching and enhance comfort.

1. Saini, K. S., Patnaik, M. M., & Tefferi, A. (2010). Polycythemia vera‐associated pruritus and its management. Eur J Clin Invest, 40(9), 828–834.
2. Lelonek E, Matusiak Ł, Wróbel T, Szepietowski JC. Aquagenic Pruritus in Polycythemia Vera: Clinical Characteristics. Acta Derm Venereol. 2018 Apr 27;98(5):496-500.
3. Siegel, F. P., Tauscher, J., & Petrides, P. E. (2013). Aquagenic pruritus in polycythemia vera: Characteristics and influence on quality of life in 441 patients. Am J Hematol, 88(8), 665–669.
4. Tefferi, A., Vannucchi, A. M., & Barbui, T. (2021). Polycythemia vera: historical oversights, diagnostic details, and therapeutic views. Leukemia, 35(12), 3339–3351.