follow @PCDSUKCreated: 20th July 2012 | Last Updated: 20th November 2017
Introduction
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Itchy skin, in the absence of any obvious dermatological condition, is a very common problem. There are many causes and a logical approach is required to help formulate a diagnosis and treatment plan. |
Aetiology
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
History
Generalised pruritus
Use a logical approach to try and ascertain a cause:
Step I: take a careful history
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Medications
- Medications can sometimes be responsible for itch
- The difficulty is confirming whether or not a particular drug is the primary cause for a patients symptoms
- Some of the drugs most commonly implicated in pruritus include morphine and other opioids, statins, ACEI, digoxin, chloroquine 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
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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
Step 2: examine the skin closely to look for dermatological conditions with subtle signs
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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
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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
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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
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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, ferritin (can be low even if FBC normal), CRP, 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 and bronchial carcinoma
- Older patients - in addition 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
Step 4: psychogenic
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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
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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
- It is relatively common in the seventh decade and beyond
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
Images
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Figure: 1 Asteatotic eczema |
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Figure: 2 Asteatotic eczema: close-up |
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Figure: 3 Pruritus with excoriations and scars This patient had no signs of a primary skin pathology causing her itch. There was a history of weight loss and the patient appeared cachectic. The patient needed thorough investigations to look for serious underlying pathology - a CXR showed a primary lung carcinoma |
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Figure: 4 Pruritus - butterfly sign In the absence of skin pathology the patient will scratch and excoriate areas of skin that can be reached. The skin of the central back cannot be reached and so is unaffected - the pattern of unaffected skin takes the shape of a butterfly |
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Figure: 5 Pruritus - severe This elderly woman scratched her skin so much that she developed large numbers of scars. No cause was found for her itch |
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Figure: 6 Notalgia paraesthetica |
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Figure: 7 Notalgia paraesthetica |
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Figure: 8 Notalgia paraesthetica |
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Figure: 9 Delusions of parasitosis Excoriations caused by patient |
Management
- Treat any underlying cause
- Provide a patient information leaflet
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General measures
- Topical agents - 1 or 2% menthol in aqueous cream is very cooling. Balneum Plus ® cream has specific anti-itch properties. 5% doxepin hydrochloride cream can be useful for localised areas of itch
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Sedative anti-histamines such as hydroxyzine (Atarax ®) 25-50 mg nocte. In addition some patients may require / tolerate smaller doses eg 10 mg tds through the day. Such treatments should be used periodically, long-term use should be avoided if possible
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Features of anxiety / depression
- Consider non-medical treatments if appropriate
- Medical - consider low dose amitriptyline (10-50 mg nocte) or doxepin (25-50 mg nocte) if no contra-indications. These treatments can sometimes help even in the absence of anxiety and depression. Such treatments should be used periodically, long-term use should be avoided if possible
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Patients with more predominant features of depression are likely to require standard doses of antidepressant medication, usually an SSRI
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Phototherapy
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In recalcitrant cases of pruritus phototherapy provided in a dermatology department will benefit some patients
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In recalcitrant cases of pruritus phototherapy provided in a dermatology department will benefit some patients
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Delusions of parasitosis and Morgellon's syndrome
- Exclude 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
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Patients need treatment with a low dose of an anti-psychotic drug, usually 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
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Pruritus associated with hepatic disease, renal disease, or malignancy can be difficult to treat
- Naltrexone and rifampicin have been reported as helpful especially in renal disease, the latter is relatively contraindicated in hepatic disease
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Cholestyramine can be effective for treating pruritus secondary to liver disease
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Brachioradial pruritus and notalgia paraesthetica
- 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
- An alternative topical treatment is 5% doxepin hydrochloride cream
- For patients failing to respond to, or tolerate topical treatments consider systemic treatment with gabapentin or low dose amitriptyline
- If there are underlying neck problems refer for physiotherapy