Phòng khám chuyên khoa da li�u - Thạc s� bác s� Hu�nh Văn Quang

Itch without rash

Itch without rash

Itching of the skin, or pruritus, may be associated with dermatological conditions, pregnancy, systemic illness or psychological disorders.

When itching is not associated with a rash, it is often difficult to identify its cause. Providing symptomatic relief only may meet a patient’s needs in the short term, but will not be in the patient’s best long-term interests unless a careful search for the cause of the itch is undertaken and the provoking factors dealt with wherever possible.

Persistent scratching of apparently normal skin will eventually produce a rash characterised by linear excoriations and/or lichen simplex chronicus, which will not resolve until the itch has been relieved.

Localised itching suggests a primary dermatological cause; however, localised itching without a rash may also be a manifestation of an underlying psychological problem. It may occur on any area of the body.

Localised itching may be the only symptom during the earliest stage of a primary dermatological condition when a rash has not been apparent to the patient (eg the first few papules of varicella, or a faint erythema of a contact dermatitis or drug eruption, before an obvious rash appears). Two common but poorly understood conditions which are characterised by intense localised itching are brachioradial pruritus (itch on one or both arms) and notalgia paraesthetica (itch just below the shoulder blade). The cause of these conditions is uncertain and treatment is difficult.

Drug reactions

Drugs can cause or contribute to an itch without rash via a number of known, postulated, and unknown mechanisms. The pruritus may be localised or generalised.

Implicated drugs: Associated drugs may alter lipid and cholesterol metabolism that is critical for skin barrier function (eg statins, gemfibrozil, cimetidine, azole antifungals such as itraconazole, protease inhibitors particularly indinavir, and retinoids), reduce skin moisture content (eg diuretics), directly trigger mast cell degranulation releasing histamine and other inflammatory mediators (see urticaria), or cause drug-induced cholestasis.

Drug-induced changes that contribute to skin dryness are more common in older persons, those on multiple drugs, and those with underlying sensitive skin. The associated itch (xerotic itch) often presents during colder, lower humidity months.

Environmental causes

External stimuli involving the skin can cause itching without a rash. These include vasodilation in the skin (such as from excessive or rough clothing, humidity and high ambient temperature), excessive sweating from any cause, and dryness of the skin (particularly in the elderly and where the skin has suffered sun damage in the past). Excessive showering with the use of harsh soaps induces dryness with consequent itching.

A common cause of generalised itching is an adverse reaction to a drug (see drug eruptions). However, generalised itching can be a presenting symptom of many serious systemic conditions. Table 1 lists the nondermatological conditions that may cause generalised itching. These must be considered before deciding that the skin is the only body system involved. Sometimes the itch might be due to drug therapy for the condition rather than the condition itself.

Generalised itching may also occur during the third trimester of pregnancy associated with cholestasis (see pregnancy rashes).

If a careful history and appropriate physical examination (including a thorough examination for scabies) do not reveal the probable cause, consider investigating for the conditions listed in Table 1.The selection of any test should be based on a suggestive history or positive clinical findings, rather than being included in a nonspecific screening type approach. The decision whether to biopsy the skin should be left to a dermatologist.

Management of itch without rash

Specific treatment of identifiable causes will not be considered in this chapter. Where relevant, separation of the patient from causative environmental factors is obviously essential.

Advise patients to:

·            keep fingernails short and, if the urge to scratch is irresistible, to use the palm to rub rather than fingers to scratch, or to pat or lightly stroke the itchy area. An ice pack may be helpful. The cycle of itch–scratch–itch should be explained

·            avoid vasodilating food and drink (eg coffee, alcohol and spices)

·            avoid heavy clothing, particularly wool, and not to overdress children

·            reduce frequency and duration of baths/showers, have cool baths rather than hot showers, add an emollient bath oil to bath water, use soap substitutes avoid overheating rooms, and humidify the atmosphere (eg by placing bowls of water in centrally heated rooms).

In placebo-controlled trials, pruritus occurs in approximately 3% to 8% of controls. However, if a drug is suspected of causing an itch it should be discontinued, where possible, for a trial period of 2 to 4 weeks. In a patient with persistent pruritus without rash, obvious cause or obviously causal drug, it can occasionally be rewarding to systematically stop or change each nonessential medication for 2 to 4 weeks and then review.

Patients should avoid vasodilating drugs and cease alcohol consumption.

Because of the antipruritic effect of cold, topical preparations may be refrigerated. If the affected skin is dry (xerotic), use moisturising agents. If the skin appears normal, use soothing lotions or creams containing menthol or camphor (see general principles of topical therapy). If these measures fail, a trial of corticosteroids is recommended, because even with apparently normal skin there may be a degree of subclinical inflammation. Use

If topical therapy fails or if the condition is severe, use

An ongoing supportive relationship with the doctor can help the patient to cope with their problem. Where psychological problems (including alcohol or drug dependence) are identified, formal counselling may be appropriate. In some cases psychiatric referral may be necessary. Pruritus itself is a very stressful symptom and can aggravate the stress of situational disturbances.

If the itch is associated with a systemic disease, treatment of the primary disorder is of primary importance. Drug therapy for the condition, rather than the condition itself, should be considered a possible cause, and the drugs ceased for a trial period if possible.

If the itch is intractable, refer to a dermatologist for ultraviolet or other therapy.

Pruritus ani is discussed elsewhere.

• < Trước
• Tiếp tục >