Pruritus: causes and management

First published July 2006, updated June 2021

Key points:

• Pruritus is common in the elderly and may be the result of skin disease, a systemic cause, medication or due to xerosis in ageing skin.
• In the absence primary skin disease, a pruritus blood screen is useful.
• Symptomatic relief with emollinets, topical steroids and antihistamines can be helpful

Pruritus is defined as the unpleasant sensation that elicits a desire to scratch. It can be classified into pruritoceptive (cutaneous in origin; eg, scabies), neuropathic (due to lesions of afferent pathways of the nervous system; eg, brain tumours), neurogenic (due to centrally acting mediators; e.g., opioid peptides of cholestasis) and psychogenic. The two major peripheral mediators in an itch are histamine and the neuropeptide substance P. Although often perceived as trivial, pruritus can be very distressing and socially disabling – resulting in serious impairment of an individual’s quality of life. Persistent pruritus occurs in up to 30 per cent of elderly people¹. It may be a result of a number of primary skin diseases, systemic diseases, medications or, when no abnormality can be found, as a consequence of the ageing process of the skin.

Xerosis

Many elderly people suffer from dry skin (xerosis). This may be as much as 75 per cent of those aged 64 years and older². A reduction in the activity of sebaceous and sweat glands, and a decrease in sterol esters and triglycerides with advancing age, may be responsible^3,4. Water loss from skin is the same as in younger individuals, but the water content of the epidermis is slightly reduced in ageing skin which may also contribute.

Itching as a result of xerosis is common in the elderly. Pruritus is usually intense and often involves the anterolateral aspect of the lower legs, back and waist, but may be generalised. Winter is a peak time for presenting with xerosis due to the low humidity in ambient air and use of heating systems that force hot, dry air into the environment.

Dry skin may present with redness, scaling or cracks. The cracks resemble those seen in fi ne antique porcelain (eczema craquelé) and are a result of the loss of hydration in the epidermis. As they extend and deepen, they form fissures that eventually reach the depth of dermal capillaries causing bleeding. Emollients close these cracks and fissures by filling spaces around desquamating (peeling) – but attached – skin flakes sealing moisture into the skin through the production of an occlusive barrier and thereby softening the skin^2,3,5.

Ingredients in emollients include mineral oils (eg, liquid paraffin, petrolatum), waxes (eg, lanolin, beeswax, carnauba), long-chain esters, fatty acids, and mono-, di- and triglycerides6 . Most preparations for dry skin use a combination of these. Emollients are the only effective treatment for xerosis-related pruritus. Systemic antihistamines and topical or systemic steroids are ineffective and should not be prescribed⁷.

Primary skin diseases

The first presentation of primary skin disease may occur in old age and cause pruritus. The following skin conditions in the elderly therefore need to be considered.

Scabies

Institutionalised care, such as nursing and residential homes, predispose the elderly patient to contagious aetiologies of pruritus. With scabies, pruritus usually occurs four to six weeks following infestation with the Sarcoptes scabiei mite. It is usually generalised, affecting all areas except the face, but is worse over the hands, forearms, thighs and genitals. Often other family or care home members have similar symptoms or have already been diagnosed with scabies.

The diagnosis is confirmed by identifying serpentiginous linear tracks (burrows) usually located along the sides of the fingers, palms or wrists. Affected individuals also typically have an erythematous papular eruption on the trunk and limbs as a result of an allergic reaction to the mite. Occasionally extensive infestations occur with the mite resulting in a myriad of burrows and crusting and scaling of the skin, which may include the face. This is termed Norwegian (crusted) scabies and is more commonly found in institutions such as nursing homes.

The most commonly used preparations to treat scabies are Malathion 0.5 per cent lotion and Permethrin five per cent cream, but numerous other preparations are available. Ivermectin at a single dose of 150-200mg/kg body weight is usually reserved for Norwegian scabies. Although treatment eradicates the mite, the itch – which is mainly due to an allergic reaction to the mite – often persists for up to a month. Topical steroids, crotamiton (Eurax) cream and emollients may be needed for symptomatic relief.

Atopic dermatitis

Late onset atopic dermatitis is uncommon. It presents with an erythematous ill-defined rash with fi ne scaling; in the acute state, it presents with oedema, vesiculation, serous exudates and crusting. It is usually symmetrical and may affect any part of the body. The mediators of pruritus in atopic dermatitis have not been clearly identified despite extensive research. Antihistamines have a limited role in relieving itch, which indicates that histamine is not the sole pruritogen. The main beneficial effects of antihistamines are thought to be from their sedative effects. For this reason sedating antihistamines are preferred, although they should be used with caution since the elderly often have co-morbidity. Emollients and topical steroids are helpful, and occasionally systemic agents are needed to control symptoms.

Allergic contact dermatitis

This is a delayed type IV hypersensitivity response to a substance on contact with the skin. It presents with an acute or subacute eczema, with intense irritation, pruritus, blistering and weeping of the skin following exposure to an allergen the patient has become sensitised to in the past. The original site of the eruption often gives a clue to the likely causative allergen. Common allergens in the elderly include topical medicaments such as antihistamines, anaesthetics aminoglycosides, lanolin and parabens. Other sensitisers include rubber in gloves and shoes, plastics in hearing aids and spectacle frames, and plants and chemicals in hair dyes. Diagnosis is made from the history and distribution of the rash, and can be confirmed by patch testing.

Urticaria

Urticaria (hives) is a common reaction pattern in which pink, itchy swellings (wheals) occur anywhere on the body as a result of mast cell degranulation. Individual wheals last less than 24 hours, but new lesions may continue to appear for days or months. Urticaria is idiopathic in most patients. However, a drug history should be obtained from all patients – especially in the elderly (who often have polypharmacy), as a drug may occasionally be responsible. Because histamine plays a primary role in the pruritus of urticaria, H1-receptor antagonists (antihistamines) improve or relieve itch in almost every patient. The dose should be carefully titrated up in the elderly.

Bullous pemphigoid

Bullous pemphigoid is a chronic immunobullous disease of the elderly presenting with tense pruritic blisters on normal or erythematous skin. However, occasionally patients may present with generalised pruritus without blisters or with a prodromal pruritic, urticarial or eczematous eruption. In limited disease, very potent topical corticosteroids may be sufficient in controlling it. However, most patients also require oral prednisolone at relatively high doses and are thus at risk of the complications of systemic steroids. Steroid sparing agents such as azathioprine or tetracyclines may be required.

Dermatitis herpetiformis

Dermatitis herpetiformis (DH) presents as a chronic pruritic papulovesicular eruption typically involving the elbows, knees, buttocks and scalp. Although the most common onset age is 30–40 years, it can present in the elderly. Dapsone is the drug of choice in the management of DH, starting with a dose of 25mg per day and titrating up if necessary. Symptomatic improvement may be noticeable in as little as 24–48 hours, but treatment may be required for months or even years.

The significant risk of haemolysis may, however, preclude its use in patients with severe ischaemic heart disease. A gluten-free diet may also help the symptoms and allow a reduction in the dose of dapsone.

Psoriasis

Although not considered to be a pruritic disorder, psoriasis is associated with variable degrees of pruritus in up to 84 per cent of patients⁷. The treatment of psoriasis in the elderly is the same as in younger patients, although systemic medication is used with more caution due to the increased risk of adverse effects.

Prurigo nodularis

This condition results from chronic and severe scratching and presents with small firm erythematous nodules, usually over extensor surfaces of the limbs or buttocks. Longstanding lesions may become verrucous, lichenified or fissured, and resolve to leave significant post inflammatory hyperpigmentation. An underlying cause for pruritus is not always found.

Antihistamines, wearing gloves at night and trimming fingernails may also be helpful. Topical or intralesional corticosteroids (if lesions are few in number) may be helpful. Occlusion with bandaging is often used in the management of nodular prurigo. If lesions are numerous, psoralen and ultraviolet An irradiation (PUVA) or ultraviolet B (UVB) phototherapy can help. In very severe cases oral thalidomide may be considered.

Pruritus without primary skin disease

The term ‘generalised pruritus’ is usually used to describe itching in the absence of dermatological disease or skin rash. Examination of the skin reveals either no abnormality or excoriations resulting from scratching. In these patients examination and investigation for an underlying cause is vital as the presence of systemic disease has been reported as high as 10–50 per cent⁸. In the absence of primary skin disease, polypharmacy as well as systemic disease, needs to be considered.

Senile pruritus

When no underlying cause for generalised pruritus can be found, the term ‘senile pruritus’ is often used. It has been suggested that this pruritus is a result of arteriosclerosis of the blood vessels that supply the nervous tissue in the skin. However in one study, 142 out of 162 elderly patients had an identifiable cause for their itching (including xerosis) and only 20 had true senile pruritus⁹. Thus, senile pruritus is a diagnosis made only by exclusion of other pathologies. Management is difficult and emollients and antihistamines alone rarely alleviate the problem. Anecdotal reports suggest that gabapentin, serotonin antagonists and UVB may attenuate itch in some of these patients.

Drugs

Opiates, aspirin, vitamin B complex and systemic retinoids are recognised to cause pruritus.

Cholestatic pruritus

Cholestasis may be a result of liver disease (eg, primary biliary cirrhosis or drugs such as erythromycin). It may be localised to the hands and feet or be a generalised itch. Cholestatic pruritus is associated with high plasma levels of bile salts, although there is no direct correlation between concentration of bile salts and itch. Medication such as cholestyramine, which lowers bile salts, may improve this type of pruritus. Hepatitis C may cause intense pruritus and should be considered, although it is less common in the elderly.

Renal pruritus

Uraemia is a common cause of pruritus in chronic renal failure. Approximately 80 per cent of patients on maintenance dialysis complain of itch^10,11. The mechanism is unknown. Renal transplantation is the only reliably effective treatment of renal pruritus. Topical steroids and antihistamines are usually of limited benefit but phototherapy with narrowband UVB may be helpful. Emollients may provide relief in those with dry skin. For localised pruritus, capsaicin 0.025 per cent cream can be tried. Parathyroidectomy in patients with secondary hyperparathyroidism may be effective in relieving pruritus.

Thyroid disease

Both hypothyroidism and hyperthyroidism may cause pruritus. The mechanisms postulated are dry skin in the former and increased skin temperature due to increased cutaneous blood flow in the latter. Correcting the underlying cause is necessary, but emollients may also be helpful – especially if dry skin is present in the hypothyroid patient.

Diabetes mellitus

Type 2 diabetes mellitus is common in the elderly but it is not a cause of pruritus. Patients are more susceptible to cutaneous infections, such as candidiasis, which may present with pruritus.

Iron deficiency

Iron deficiency is a common finding in the elderly, which may occur with or without anaemia and be the cause of generalised pruritus. It is often the result of a poor diet, but an underlying malignancy must be excluded if it presents with anaemia.

Polycythaemia rubra vera

Polycythaemia rubra vera presents with itching after a warm bath or shower (aquagenic pruritus), and this symptom may precede the diagnosis by several years¹². Bathing by regional sponging may help although antihistamines have a limited role. Successful treatment of the polycythaemia may not relieve the itch. Correction of venesection-induced iron deficiency may be helpful, but there is a risk it may worsen the underlying polycythaemia. PUVA is sometimes successful.

Malignancy

Intense prolonged generalised pruritus may precede the diagnosis in Hodgkin’s lymphoma and indicate a poorer prognosis¹³. Other malignancies do not usually present with pruritus, but itching may be a feature in any visceral or haematological malignancy. Unfortunately, senile pruritus and xerosis are common in the elderly who as a group are also more at risk of malignancy. It is therefore only after considerable consideration of other causes that a patient should be screened for an underlying malignancy. In a six-year follow-up study of 125 patients with generalised pruritus, no significant overall increase in malignant neoplasms was found (the mean age of patients in this study was 46 for women and 63 for men¹⁴).

Brachioradial pruritus

Brachioradial pruritus (BRP) presents as a localised itch over the lateral aspect of one or both arms, and less commonly on the shoulders and upper trunk. Symptoms show strong seasonal variation with itch exacerbated by exposure to strong sunlight in the summer. It has been suggested BRP results from sunlight-induced damage to cutaneous nerve endings or rarely by cervical root damage due to degenerative arthropathy, cervical rib or spinal tumours. BRP is often refractory to topical or oral corticosteroids and antihistamines, but topical capsaicin cream or gabapentin may be helpful.

Psychological

A variety of psychological disorders may present with itching. These include depression, anxiety disorders, obsessive-compulsive disorder, personality disorder, psychosis and eating disorders. Parasitophobia is a delusion of parasitic infestation of the skin and usually presents with pruritus alone. Patients may bring in particulate material they believe represents the parasites or insects causing the itch. Treatment is rarely successful and usually involves antidepressant and anxiolytic drugs along with a psychiatric referral. Pimozide is a phenothiazine that has been specifically advocated for the treatment of delusions of parasitosis¹⁵.

Treatment

The most important step in the management of pruritus is to identify and treat any underlying cause. A pruritus screen (Table 1) may be helpful in this. Symptomatic relief is the next step, and even more vital if a cause for the itch cannot be identified. General measures such as keeping the environment cool, wearing cotton light clothing and bedclothes, and using cooler water when bathing may be helpful. Emollients, one to two per cent menthol in aqueous cream, topical corticosteroids and oral low-sedating antihistamines can also provide symptomatic relief – although the latter must be used with caution in the elderly. Ultraviolet light (PUVA or UVB) treatment is most effective in pruritus secondary to inflammatory dermatoses, chronic renal failure, primary biliary cirrhosis, polycythaemia rubra vera and prurigo nodularis. Systemic tricyclic antidepressants have been shown to be helpful in some patients with intractable itching. More recently, the use of opioid-receptor antagoinists (eg, naloxone)¹⁶ and selective serotonin reuptake inhibitors (eg, paroxetine)¹⁷ in intractable pruritus have shown promising results. Further research into the neurophysiological pathways for itch should lead to better management of pruritis.

Pruritus increases in incidence with age and may be due to a primary cutaneous disorder or be a symptom of an underlying systemic disease. In the absence of primary skin disease, polypharmacy as well as systemic disease need to be considered.

Table 1. Screening for treatment 

References 

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13. Feiner AS, Mahmood T, Wallner SF. Prognostic importance of pruritus in Hodgkin’s disease. JAMA 1978; 240: 2738-40
14. Paul R, Paul R, Jansen CT. Itch and malignancy prognosis in generalised pruritus: a 6- year follow-up of 125 patients. J Am Acad Dermatol Am Acad Dermatol 1987;16: 1179-82
15. Newbold PCH. Antidepressants and skin disease. BMJ 1988; 298: 379
16. Taddese A, Nah SY, McCleskey EW. Selective opioid inhibition of small nociceptive neurones. Science 1995; 270: 1366-9
17. Zylicz Z, Smits C, Krajnic M et al. Paroxetine for pruritus in advanced cancer. J Pain Symptom Manage 1998; 16: 121-4