Pruritus may be due to skin disorders, drugs, certain systemic diseases, or psychiatric or neurological disorders.
It is important to look for signs of any specific skin disorder, and to assess whether the skin findings are secondary to scratching or picking or whether the pruritus is only subjective (in the absence of skin findings).
If there are no significant skin findings, look for pruritus due to dry skin (asteatosis), dermographism or drug-induced pruritus.
Causes of pruritus
Pruritus originating from the skin
Dry skin (asteatosis)
This is a common cause of pruritus in the elderly. There is not necessarily any visible skin abnormality.
Most common during the winter months, often in the lower limbs. Predisposing factors include advancing age, frequent washing, dry room air and possibly a history of atopy.
Drugs may cause pruritus through a variety of mechanisms, such as allergic reactions (immunological mechanism), hypersensitivity reactions (pharmacological or other mechanism, such as release of histamine), dry skin, increased photosensitivity (see also Photodermatitis and drug-induced photodermatitis Photodermatitis), liver damage or cholestasis.
Virtually any medicine may cause pruritus. In most cases, there is a clear temporal association, but in some cases pruritus may begin after a long period of use or with delay after exposure.
Medicines that typically cause pruritus include
beta-lactam antibiotics, in particular penicillins and cephalosporins (pruritus, skin reactions, cholestasis)
other antimicrobials, such as sulpha drugs, quinolones, tetracyclines, metronidazole
statins (mechanism not fully understood, cholestasis)
opioids (release of histamine, central effect)
NSAIDs (increased leukotriene synthesis)
allopurinol
sulfonylureas
chloroquine or hydroxychloroquine (mechanism unclear, most common in people with dark skin, rare in white people)
many anticancer drugs (such as cytotoxic drugs, tamoxifen)
hydroxyethyl starch (pruritus typically beginning 3-4 weeks after i.v. treatment).
Pruritus of systemic disease
Systemic diseases are not necessarily manifested on the skin, but they may alter the superficial skin structure (e.g. dry skin in patients with hypothyroidism) or colour (e.g. jaundice in patients with cholestasis), and there may also be secondary signs of scratching due to pruritus.
Kidney disease
Renal failure may cause pruritus.
Pruritus associated with uraemia is a common problem in patients undergoing dialysis.
Pruritus is a major general symptom in several haematological malignancies, more rarely in solid tumours.
Haematological diseases associated with pruritus include lymphomas Lymphomas (affects about one in three patients with Hodgkin's lymphoma) and polycythaemia vera Polycythaemia Vera (Pv).
This is always an exclusion diagnosis made after thorough clinical examination and appropriate investigations.
The cause of pruritus may be psychiatric (such as depression, bipolar disorder, psychosis, use of intoxicants, schizophrenia).
Pruritus may result from a vicious circle of itching and scratching (neurodermatitis, pictures 234) or represent a somatoform symptom (such as pruritus as a symptom of depression), an artefactual clinical picture (self-inflicted scratch marks) or psychosis (such as delusional parasitosis, schizophrenia).
Pruritus of another cause may be aggravated or become chronic for psychological reasons.
Pruritus should always primarily be suspected of being caused by a specific skin disorder (the most common cause).
There are no diagnostic tests available for drug-induced pruritus. Therefore, the diagnosis should be based on temporal association between starting to take the drug and the onset of pruritus.
In unclear cases, it is often necessary to withdraw the drug for some time (e.g. 6 weeks), during which any drug-induced pruritus will usually be alleviated.
If the pruritus is caused by a systemic disease or a malignancy, patients often have other symptoms, as well (such as weight loss or enlarged lymph nodes).
Any psychiatric or neurological causes should always be defined by exclusion of other diagnoses.
Patient history
Is this an acute or a chronic problem? Aggravation of a pre-existing skin disorder?
Does the patient have a history of skin disorders; is there a family history of skin disorders such as atopic eczema or psoriasis?
Does the patient have any diagnosed contact allergy? Has the patient reacted to cosmetics or skin care products, for example?
Are the lesions itchy (atopic eczema, allergic contact dermatitis)?
Do any of the patient's contacts have pruritus (scabies)?
Does the patient have pain or systemic symptoms (systemic disorders)?
Skin lesions should be examined close-up, too, paying attention to the following:
Location (symmetric?, unilateral?, main sites affected?)
Are the lesions scaly (suggesting an eczematous disease, itching due to dry skin, psoriasis); are there wheals?
Are the lesions clearly defined? Are there erythematous spots, blisters or blister surfaces?
Situation in other skin areas (the scalp, nails, genital area, oral mucosa)
A thorough physical examination (jaundice, thyroid gland, lymph nodes)
Psychiatric state, signs of depression, anxiety, health anxiety?
Medical and drug history
Travel history, symptoms in other family members
Associated signs (fever, weight changes, night sweats)
Findings
Skin findings specific for skin disorders
Diagnosis is usually based on the clinical picture, course of disease and history.
Treatment and examinations depend on the skin disorder.
Unspecific, secondary findings
Linear wounds caused by scratching the skin (excoriations), thickening of the skin due to scratching (lichenification), nodules caused by skin picking (prurigo nodules)
Even in this case, there is often a specific skin disorder (even in the absence of specific skin findings)
In pruritus due to systemic diseases (such as malignancies or renal failure), secondary scratch marks can be seen (often only in the areas that the patient can reach).
Psychogenic causes
Generalized pruritus in the absence of skin findings
If an itching patient does not have any skin findings at all, one of the following should primarily be suspected:
pruritus due to dry skin (asteatosis);
atopic pruritus (may occur also in the absence of specific skin symptoms);
dermographism and urticarias;
drug-induced pruritus.
Systemic somatic disorders should be excluded, as necessary.
Local pruritus
Despite being local, the pruritus may be due to a skin disorder or a systematic disorder.
May be associated with nerve damage or neuropathy (e.g. diabetic neuropathy).
Notalgia paraesthetica (itching of the mid back; picture 38)
Neurodermatitis (often on the legs, neck, genital area; caused by a vicious circle of itching and scratching; may begin after a preceding skin disorder has healed)
Psychogenic pruritus (psychiatric and neurological disorders)
Workup
If pruritus due to a systemic disease is suspected (usually showing other symptoms in addition to itching), some of the following tests may be performed.
Laboratory tests
Initial tests, as appropriate: full blood count, ESR, fasting plasma glucose, CRP, TSH, creatinine, ALT, alkaline phosphatase, bilirubin (total and conjugated)
Possible further investigations include ferritin, serum IgE, serological IgE screening for the most common inhaled allergens, hepatitis serology, HIV test, skin antibodies or pemphigoid antibodies, for example.
Imaging
Chest x-ray (hilar status; lymphomas?)
Ultrasonography of lymph nodes, the spleen and the liver (lymphomas?)
More specific further examinations can be performed based on the results, clinical picture and course of disease, as necessary.
Symptomatic treatment of pruritus
Treatment should primarily be symptomatic.
The treatment of various skin disorders is discussed in the relevant articles.
Most patients benefit from symptomatic treatment even if the cause of pruritus remains unclear.
If the reason remains unclear, the patient should be reassessed every now and then and referred for further examinations, as necessary.
Non-pharmacological treatment
If the itching is due to dry skin, the skin should be moisturized with non-medicated ointments and drying detergents should be avoided.
Hot air and the sun should be avoided, the skin washed with lukewarm rather than hot water, soap / drying detergents should be avoided and a non-medicated ointment should be used.
Clothes irritating the skin (wool and other coarse materials) should be avoided, unscented detergents used and the skin patted dry.
The vicious circle of scratching should be broken (by covering the scratched skin area, cutting the nails, wearing cotton gloves for the night).
Often effective in the treatment of pruritus and skin disorders
Potency to be chosen as dictated by the skin disease and the area to be treated; see disease-specific instructions
For experimental treatment of pruritus of an unclear cause, intermittent treatment with a mid- to high potency glucocorticoid cream once or twice daily for periods of 2-3 weeks, for example
In addition, they can be used for the treatment of many other types of pruritus (e.g. uraemic pruritus).
Experimental intermittent treatment or initial treatment twice daily until the situation calms down and subsequently twice a week, as necessary
Cooling creams
Menthol cream several times a day, as necessary
Prescribe a cream containing, for example, 1.0-2.0 g levomenthol made up to 100.0 g with a moisturizing basic cream. The ointment alleviates pain and itching and should be spread on the skin several times a day.
Menthol rubbing alcohol (prescription free, to be spread on itchy skin areas 2-3 times daily)
For symptomatic treatment of pruritus of unclear cause
Non-sedating antihistamines are effective against pruritus caused by urticaria or dermographism. It is worthwhile to try them also in pruritus caused by other reasons. Their dose can be increased 2- to 4-fold depending on the response; e.g. one to two 10-mg cetirizine tablets once or twice daily (notice local regulations regarding exceptional dosage when making the prescription).
Hydroxyzine 25-50 mg at night is often helpful. If necessary, a dose of 25 mg 3-4 times daily may be used (provided that no excessive tiredness occurs).
In selected cases, doxepin (with an antihistamine effect), usually starting with 10-20 mg in the evening and gradually increasing the dose, for example by 10 mg every 1-2 weeks, until the target dose of 30-(50) mg in the evening is reached.
SSRIs (such as paroxetine, sertraline, fluvoxamine) may help. There is evidence for the efficacy of paroxetine at an initial dose of 20-30 mg daily, for example; the dose can be increased up to 40-50 mg daily, as necessary. The initial dose of sertraline is 50 mg, after which the dose may be increased, if needed, up to 75-100-(200) mg.
A low dose of a sedating antidepressant (for example mirtazapine, amitriptyline, nortriptyline) may also be a good alternative. For mirtazapine the initial dose is 7.5-15 mg in the evening, and the dose can be increased up to 30 mg in the evening, as necessary. The initial dose of amitriptyline is 10-25 mg in the evening, maintenance dose 25-50 mg in the evening.
For nocturnal pruritus, some patients may need intermittent hypnotics, such as benzodiazepine derivativesor short-acting benzodiazepines.
For short-term treatment of severe cases, oral glucocorticoids, such as 20 to 40 mg prednisolone every morning for 1 to 2 weeks, can be considered.
Light therapy (such as SUP, narrowband UVB, bath PUVA) can be considered in severe cases.
Also SSRI drugs and sedative antidepressants have been used in the treatment of uremic, cholestatic and paraneoplastic pruritus.
For the treatment of pruritus in terminally ill patients, see also Palliative Treatment.
Specialist consultation
A dermatologist should be consulted if the basic examinations of a patient with unclear pruritus do not reveal the cause and appropriate symptomatic treatment does not help.
In severe pruritus, a dermatologist should be consulted if a specific skin disorder is suspected or light therapy is being considered (e.g. uraemic pruritus, dialysis).
If pruritus is suspected of being due to a systemic disease, an internist (such as a haematologist) should be consulted.
Psychogenic pruritus should be treated by a psychiatrist.
References
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Reich A, Ständer S, Szepietowski JC. Drug-induced pruritus: a review. Acta Derm Venereol 2009;89(3):236-44. [PubMed]
Frese T, Herrmann K, Sandholzer H. Pruritus as reason for encounter in general practice. J Clin Med Res 2011;3(5):223-9. [PubMed]
Berger TG, Shive M, Harper GM. Pruritus in the older patient: a clinical review. JAMA 2013;310(22):2443-50. [PubMed]
Yosipovitch G, Bernhard JD. Clinical practice. Chronic pruritus. N Engl J Med 2013;368(17):1625-34. [PubMed]
Kouwenhoven TA, van de Kerkhof PCM, Kamsteeg M. Use of oral antidepressants in patients with chronic pruritus: A systematic review. J Am Acad Dermatol 2017;77(6):1068-1073.e7. [PubMed]
Simonsen E, Komenda P, Lerner B ym. Treatment of Uremic Pruritus: A Systematic Review. Am J Kidney Dis 2017;70(5):638-655. [PubMed]
Kouwenhoven TA, van de Kerkhof PCM, Kamsteeg M. Use of oral antidepressants in patients with chronic pruritus: A systematic review. J Am Acad Dermatol 2017;77(6):1068-1073.e7. [PubMed]