Pruritus (itch) - without a rash

Patient Information Leaflet
Link: Itch (pruritus) without a rash

https://www.pcds.org.uk/patient-info-leaflets/itch-pruritus-without-a-rash

Generalised itch in the absence of any obvious dermatological condition is a very common problem with a prevalence of approximately 17% in adults and perhaps 50% or higher in the elderly. There are many causes and a logical approach is required to help formulate a diagnosis and management plan.

This chapter is set out as follows:

The causes of pruritus can be grouped as follows:

Generalised pruritus

• Medications
• Aquagenic pruritus 
• Dermatological conditions with subtle signs 
• Systemic disease
• Psychogenic (including delusions of parasitosis)
• Idiopathic 

Localised pruritus 

• Brachioradial pruritus
• Notalgia paraesthetica

Generalised pruritus 

Use a logical approach to try and ascertain a cause:

Step I: take a careful history

• Medications
• Medications can sometimes be responsible for itch
• The difficulty is confirming whether or not a particular drug is the primary cause for a patient's symptoms
• Some of the drugs most commonly implicated in pruritus include morphine and other opioids, statins, ACEI, NSAIDs, digoxin, antimalarials and sulphonamides
• The only way of knowing if the drug is responsible is by discontinuing the medication for a few weeks (if possible) and seeing if symptoms improve

• Aquagenic pruritus
• Patients complain of an intense pricking itch on contact with water or change of skin temperature, but do not develop a rash
• The condition tends to respond poorly to treatment with antihistamines but may respond to phototherapy
• Can predate polycythaemia rubra vera by 5 years so patients require an annual FBC

• Underlying systemic cause
  • Undertake a systemic enquiry to look for any diagnostic clues

Step 2: examine the skin closely to look for dermatological conditions with subtle signs 

• Dermographic urticaria 
• ​Patients develop a red, raised rash along scratch marks after itching
• If responsible for the itch, such patients should respond to non-sedating antihistamines

• 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, preferably ointments

• Scabies
  • ​Scabies is usually obvious, however, occasionally it can be more subtle
  • Check for burrows, which are most common on the sides of fingers, the webs, the borders of the hands, the wrists and the feet, as well as papules and nodules, which are most commonly seen on the shaft of the penis (pathognomonic), the groins and in the axillae

Step 3: systemic disease - a wide range of illnesses can be responsible for pruritus 

• ​Liver disease, renal failure, haematological disorders (eg iron deficiency anaemia, polycythaemia, Hodgkin’s lymphoma), thyroid disease and paraneoplastic phenomena can all cause itch

• 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

• Refer to the section on investigations for more information 

Step 4: psychogenic

In the absence of any organic cause look for underlying psychological problems: 

• Anxiety / depression can be the cause of pruritus, especially in older patients. Long-standing itch can also cause depression

• Delusions of parasitosis and Morgellon's syndrome
  • ​These are true psychotic disorders
  • In delusions of parasitosis patients are convinced that a parasite / infestation is living in their skin
  • In Morgellon's syndrome patients report fibres coming out of their skin 
  • Both groups often complain of a crawling sensation 
  • The patient often brings to the consultation inorganic matter, which they truly believe is the organism / fibre 
  • Examination often shows excoriations but no primary underlying skin abnormalities such as burrows or urticated papules
  • The first sample brought to the surgery should be sent for microscopy, rather than being dismissive of the patients view. For more information refer to the section on management

Step 5: no identifiable cause  

• Up to 50% of patients will have no clear cause for their itch and can be termed as having idiopathic pruritus, a diagnosis of exclusion 
• It can cause persistent and widespread itching and is often associated with extensive excoriation

Localised pruritus 

• Brachioradial pruritus and notalgia paraesthetica are two well-defined conditions causing localised areas of itching / burning

• Brachioradial pruritus refers to an area around the elbow and extensor surface of the arm

• Notalgia paraesthetica refers to the mid-scapular area

• The aetiology is possibly that of a sensory neuropathy. Some cases of brachioradial pruritus are thought to be secondary to cervical pathology 

All patients with generalised pruritus who do not have an obvious dermatological cause for their itch require the following: 

• Standard screen - FBC and ferritin, CRP, routine biochemistry (U&E, creatinine, LFT, bone, TFT), antimitochondrial antibody (to rule out primary biliary cirrhosis), urinalysis, a CXR to help exclude lymphoma and bronchial carcinoma
   
• Patients with generalised pruritus and suspicion of haematological involvement also require a blood film, lactate dehydrogenase (can be a marker of lymphoma), and ESR (if available). Immunoglobulins and urinary paraproteins may also be requested, but will have a low yield, as myeloma is rarely associated with generalised pruritus 

Investigations for suspected solid tumours:

One study identified the risk of manifesting any malignancy as significantly higher in the first three months after developing itch. In general, healthy patients with normal screening blood tests do not require detailed investigations to look for internal malignancy, however, the following groups of patients will require further investigations -

• Patients with relevant findings on systemic enquiry or physical examination require investigations tailored to their symptoms/signs
   
• Patients with new onset (within three months) severe and persistent pruritus should, in the absence of any obvious trigger or other symptoms or signs or abnormal basic investigations, be considered for a CT scan of the neck, chest, abdomen and pelvis. Also consider a scan for patients with significantly elevated LDH levels at presentation (>1.5 times upper limit of normal), and those with increasing LDH levels  

Other investigations to be considered:

• HIV and hepatitis serology - especially in those at higher risk
   
• Foreign travel and tropical disease - consider parasitic infection, especially in the presence of a blood eosinophilia. The most common parasites that induce itch are the helminths such as Strongyloides stercoralis

Additional notes:

• Iron-deficiency anaemia - is usually demonstrated by a low ferritin level, however, ferritin is an acute-phase protein and so may be ‘artificially’ raised. If iron deficiency anaemia is suspected (eg low haemoglobin / microcytosis), but yet ferritin levels are normal check serum iron and total iron binding capacity. Those who have unexplained iron deficiency should also be tested for tissue transglutaminase (TTG) antibodies to look for coeliac disease, if this is abnormal the patient should be referred to a gastroenterologist for consideration of endoscopy and small bowel biopsy
   
• Polycythaemia vera (PV) - should be considered in the presence of a raised haemoglobin or haematocrit, especially in association with microcytosis (suggesting secondary iron deficiency), raised white cell or platelet count. Patients with suspected PV should be referred to haematology

Generalised pruritus 

General management

• Treat any underlying cause. If no cause is found and the symptoms remain moderate-severe / recalcitrant then remain vigilant to the possibility of a late presenting paraneoplastic condition, especially lymphoma, in such cases monitor FBC and LDH (lactate dehydrogenase) as increasing levels are a marker of lymphoma

• Refer to the top right of the page for a patient information leaflet available through a QR code or printable PDF

Topical agents 

• 1 or 2% menthol in aqueous cream is very cooling. E45 Itch Relief ® cream and Balneum Plus ® cream have specific anti-itch properties. 5% doxepin hydrochloride cream can be useful for localised areas of itch

• In elderly patients with very dry skin use an emollient ointment as a moisturiser, and a trial of a topical steroid if asteatotic eczema is suspected 

Anti-histamines

• A four-week trial of non-sedating antihistamines such as fexofenadine 180 mg or loratadine 10 mg, or mildly sedative agents such as cetirizine 10 mg are now preferred to sedative drugs such as chlorpheniramine and hydroxyzine. If there is no improvement consider increasing the dose, it is safe to take up to 4 a day if needed. While there is no clear rationale for non-sedating antihistamines in any condition other than urticaria, they are listed in the British Association of Dermatologist guidelines as a treatment for pruritus, however, if there is no significant improvement then the medication should be stopped

• If sedating antihistamines are prescribed they must only be used periodically, as there is a possible association between long-term sedating antihistamines and dementia 

Other systemic treatments to consider

• Gabapentin / pregabalin
• A minimum of a six-week trial (if the patient is able to tolerate the treatment)
• Gabapentin - small doses can be effective eg 100 mg OD to TDS, gradually increasing up to 300 mg TDS if needed. Gabapentin can be increased up to 600 mg three times a day over 3–4 weeks if there is no effect at a smaller dose
• Pregabalin - start at 75 mg twice daily and increase to 150 mg twice daily if needed

• Antidepressants
  • SSRI's and mirtazapine have been used with success in some patients with generalised pruritus

Phototherapy

• In recalcitrant cases of pruritus, phototherapy provided in a dermatology department will benefit some patients

Specific types of pruritus 

Brachioradial pruritus and notalgia paraesthetica (and other areas of localised itch)

• ​Consider Capsaicin ® cream 0.075% cream. Apply thinly once a day and increase gradually up to a maximum of four times a day (or whatever the patient can tolerate) over a period of two weeks. Treat for eight weeks. If the patient cannot manage 0.075% try 0.025% cream

• Topical treatment with either 5% doxepin hydrochloride cream or Eurax 10% cream

• For patients failing to respond to, or tolerate topical treatments consider systemic treatment with gabapentin or low dose amitriptyline (as above under generalised pruritus) 

• If there are underlying neck problems refer for physiotherapy

Delusions of parasitosis and Morgellon's syndrome

• Undertake a routine haematological and biochemical blood screen, and check B12 levels. Additionally, exclude other organic disease such as substance misuse, a brain tumour or dementia

• Patients are best referred to a psychodermatology clinic, although in the UK these are limited. Alternatively, refer to psychiatry or dermatology - check with local guidelines 

• ​Patients need treatment with a low dose of an anti-psychotic drug such as Risperidone. Compliance is improved if the patient is approached in a non-confrontational manner, and it is explained that the medication is being used to help reduce the unusual sensations in the skin caused by these conditions  

Pruritus associated with hepatic disease, renal disease, or malignancy can be difficult to treat

• ​Rifampicin, cholestyramine and naltrexone have all been used to treat pruritus associated with hepatic disease 

• Refer to the BAD guidelines on Generalised Pruritus for more details on treating specific causes of pruritus (see below)

• Refer to the BAD guidelines on Generalised Pruritus