Primary Care Dermatology Society
The leading primary care society for dermatology and skin surgery

Pruritus (without a rash)

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Latest update 16/07/2010

This chapter is set out as follows:

Introduction

  • Itchy skin a is very common symptom, especially as people get older
  • There are many different causes
  • It is important to take a good history and examination, and then investigate further where appropriate

The causes of pruritus

Causes of pruritus can be grouped as follows:

  • Skin disease
  • Systemic disease
  • Medications
  • Psycogenic (including delusions of parasitosis)
  • Localised e.g. brachioradial pruritus and nostalgia paraesthetica
  • Idiopathic

Skin disease

This section does not cover obvious rashes responsible for itch such as atopic eczema and chronic ordinary urticaria, but instead more subtle presentations of skin disease

  • Dermographic urticiaria - patients develop a red palpable rash along scratch marks after itching. Symtpoms should be reproducible and so try and induce symptoms, if positive the patient should respond to non-sedating antihistamines
  • Aquagenic pruritus - patients compain of an intense pricking itch on contact with water or change of skin temperature, but do not develop a rash. The condition tends to responds poorly to treatment with antihistamines but may respond to light therapy
  • Dry skin (xerosis) / asteatotic eczema - a common cause of pruritus, especially in the elderly in winter. Signs may be subtle, look closely for fine scale. Treatment is with copious amounts of moisturisers
Figure 1 – Dry, asteatotic eczema

Systemic disease

  • A wide range of illnesses can be responsible for pruritus including:
    • Liver disea se
    • Renal failure
    • Haematological disorders - iron deficiency anaemia, polycythaemia, Hodgkin’s lymphoma
    • Thyroid disease
    • Paraneoplastic phenomena
  • In absence of signs of skin disease patients require a thorough history and an examination that should place special emphasis on examining for enlarged lymph nodes and hepatosplenomegaly. Investigations should include:
    • Standard screen - FBC, PV/ESR, ferritin (can be low even if FBC normal), routine biochemistry (U&E, creatinine, LFT, bone, TFT and glucose), antimitochondrial antibody (to rule out primary biliary cirrhosis), urinalysis, and a CXR to help exclude lymphoma
    • Older patients – in addtion to the above check immunoglobulins and plasma electrophoresis
    • Further detailed investigations / referral is likely to be warranted for patients with significant weight loss or any other red flags that could suggest a paraneoplastic phenomena or other potentially serious cause

Figure 2 – Pruritus with excoriations and scars

This patient had no signs of a primary skin disease causing her itch. There was a history of weight loss and the patient appeared cachetic. The patient was investigated thoroughly

Medications

  • Medications can sometimes be responsible for itch
  • The difficulty is in confirming whether or not a particular drug is the prime cause for a patients symptoms
  • Some of the drugs most commonly implicated in pruritus include morphine and other opioids / statins / ACEI / digoxin / chloroquine / sulphonamides
  • The only way of knowing if the drug is responsible is by discontinuing the medications for a few weeks (if possible) and seeing if the symptoms improve

Psycogenic

  • Anxiety / depression can be the cause of pruritus or can result from long-standing pruritus. The following treatments should be considered:
    • Non-medical treatments if appropriate
    • Medical – where anxiety / depression appear to be part of the problem consider low dose amitriptyline (25 to 75mg nocte) or doxepin (10-50mg nocte). Patients with more predominant features of depression are likely to require standards doses of antidepressant medications
  • Delusions of parasitosis
    • Is a psychotic disorder
    • Presentation – patients are convinced that a parasite / infestation is living in their skin. The patient often brings to the consultation inorganic matter, which they truly believe is the organism responsible
    • Examination – often shows excoriations but no primary underlying skin abnormalities such as burrows or urticated papules
    • Management – is with anti-psycotic drugs. Patients are best referred to a psychiatrist, although they rarely agree to attend

Localised

  • Brachioradial pruritus and notalgia paraesthetica
    • These are two well-defined conditions causing localised areas of an itching / burning
    • Brachioradial pruritus refers to an area around the elbow and extensor surface of the forearm, notalgia paraesthetica refers to the mid-scapular area
    • Aetiology - possibly caused by a sensory neuropathy, or in the case of brachioradial pruritus chronic UV damage
    • Treatment – consider Capsaicin ® cream 0.075% cream. Apply thinly OD and increase gradually up to a maximum of 4 times a day (or whatever the patient can tolerate) over a period of two weeks. Treat for 8 weeks. If the patient cannot manage 0.075% try 0.025%. For patients failing to respond to topical treatments consider systemic treatment with low does amitriptyline or gabapentin

Idiopathic

These are diagnoses of exclusion and include:

  • Pruritus of the elderly (syn. senile pruritus) - persistent and widespread itching, often associated with extensive excoriation, is relatively common in the 7th decade and beyond
  • Postmenopausal pruritus – tends to provoke rubbing more than scratching

General notes on management

  • Treat any underlying cause
  • General:
    • Topical agents - 1 or 2% Arjun ® cream (menthol in aqueous cream) is very cooling. Balneum plus ® cream has specific anti-itch properties
    • Sedative anti-histamines such as Atarax ® (hydroxyzine) 25-50mg nocte. Some patients may also tolerate smaller does e.g. 10mg tds through the day, but assess risk of falls. Use periodically otherwise tolerance may develop
    • Phototherapy provided in a dermatology department will benefit some patients
    • Gabapentin up to 2g in divided doses can be useful for some patients
  • Pruritus associated with hepatic, renal disease, or malignancy can be difficult to treat. Naltrexone and rifampicin have been reported as helpful especially in renal disease although the latter is relatively C-I in hepatic disease. Cholestyramine can be effective for treating pruritus secondary to liver disease