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Pronunciations atopic atopic dermatitis barbiturates corticosteroid dermatitis diphenhydramine eosinophil granuloma hydrocortisone hydroxyzine ichthyosis lymphoma pruritus psoriasis rosacea toxic epidermal necrolysis tretinoin

Itching (pruritus) is a sensation that instinctively demands scratching.

Itching may be caused by a skin disorder or by a disease that affects the whole body (systemic disease). Skin disorders that cause severe itching include infestations with parasites (such as scabies, mites, or lice), insect bites, hives, atopic dermatitis, and allergic dermatitis and contact dermatitis. These disorders usually also produce a rash. Systemic diseases that can cause itching include liver disease, kidney failure, lymphomas, leukemias and other blood disorders, and, occasionally, thyroid disease, diabetes, and cancer. However, itching from these diseases usually does not result in a rash.

Many drugs can cause itching, including barbiturates, morphine and aspirin as well as any drug to which a person has an allergy.

Itching is also common during the later months of pregnancy. Usually, pregnancy-related itching does not indicate any abnormality, but it can result from mild liver problems.

Often, contact with wool clothing or irritants, such as solvents or cosmetics, causes itching. Dry skin (xerosis), which is especially common among older people, can cause severe, widespread itching. Dry skin also can result from cold weather or prolonged exposure to water. Hot baths typically worsen itching.

The act of scratching can itself irritate the skin and lead to more itching, creating an itching-scratching-itching cycle. Vigorous scratching may cause redness and deep scrapes in the skin. In some people, even gentle scratching causes raised, red streaks that can itch intensely. Prolonged scratching and rubbing can thicken and scar the skin.

When the Skin Is Dry Normal skin owes its soft, pliable texture to its water content. To help protect against water loss, the outer layer of skin contains oil, which slows evaporation and holds moisture in the deeper layers of skin. If the oil is depleted, the skin becomes dry. Dry skin (xerosis) is common, especially among people past middle age. Common causes are cold weather and frequent bathing. Bathing washes away surface oils, allowing the skin to dry out. Dry skin may become irritated and often itches—sometimes it sloughs off in small flakes and scales. Scaling most often affects the lower legs. Rubbing or scratching dry skin can lead to infection and scarring. Dry Skin A form of severe dry skin is called ichthyosis. Ichthyosis can be an inherited disorder or can result from a number of other medical problems, such as an underactive thyroid gland, lymphoma, and AIDS. The key to treating simple dry skin is keeping the skin moist. Taking fewer baths allows protective oils to remain on the skin. Moisturizing ointments or creams containing petroleum jelly, mineral oil, or glycerin also can hold water in the skin. Harsh soaps, detergents, and the perfumes in some moisturizers irritate the skin and may further dry it. When scaling is a problem, solutions or creams containing salicylic or lactic acid or urea may help remove the scales. For some forms of severe ichthyosis, creams containing substances related to vitamin A, such as tretinoin Some Trade Names RETIN-A AVITA RENOVA , help the skin shed excessive scales.

Diagnosis

Doctors try to determine the cause of itching to eliminate it. Often, the cause is obvious, such as an insect bite or poison ivy. Itching that lasts longer than a few days or that comes and goes frequently without an obvious cause usually requires testing. If an allergy is suspected, skin tests may be performed (see Allergic Reactions: Symptoms and Diagnosis and Diagnosis and Treatment of Skin Disorders: Skin Tests). If a systemic disease is suspected, blood tests are usually performed to check liver function, kidney function, and blood sugar levels. The number of eosinophils, a type of white blood cell, may be checked as well, because a high number may indicate an allergic reaction. Sometimes, the doctor may have a person discontinue one or more drugs to see whether the itching is relieved. A biopsy, in which a small piece of skin is surgically removed for examination under a microscope, or skin scraping (see Diagnosis and Treatment of Skin Disorders: Diagnosis) may help identify the cause, including an infectious one.

Treatment

For itching of any cause, bathing should be kept brief and preferably in cool or lukewarm water with very little or no soap. The skin should be patted dry gently rather than rubbed vigorously. Many people with itching benefit from an over-the-counter moisturizing cream applied right after bathing. The moisturizer should be odorless and colorless, because additives that provide color or scent may irritate the skin and may even cause itching. Fingernails, especially children's, should be kept short to minimize abrasions from scratching. Coating the affected area with soothing compounds, such as menthol, camphor, chamomile, eucalyptus, or calamine, also may help.

Taking antihistamines by mouth may decrease itching. Some antihistamines, such as hydroxyzine Some Trade Names
ATARAX
VISTARIL
and diphenhydramine Some Trade Names
BENADRYL
NYTOL
SOMINEX
, usually cause sleepiness and dry mouth and are mainly used at bedtime. Other antihistamines, such as loratadine Some Trade Names
CLARITIN
and cetirizine Some Trade Names
ZYRTEC
, usually do not cause sleepiness. Generally, creams containing antihistamines (such as diphenhydramine Some Trade Names
BENADRYL
NYTOL
SOMINEX
) should not be used, because they themselves can cause an allergic reaction.

Corticosteroid creams decrease inflammation and control itching and may be used when itching is limited to a small area. Itching from some conditions, such as poison ivy, may require high-strength corticosteroid creams. However, only mild corticosteroids, such as 1% hydrocortisone Some Trade Names
See Cortisol
, should be applied to the face, because stronger corticosteroids may thin the sensitive skin in this area. Also, powerful corticosteroid creams applied over large areas or for a long time can cause serious medical problems, especially in infants, because these drugs are absorbed into the bloodstream. Corticosteroids taken by mouth are sometimes used when large areas of the body are involved.

Specific treatments may be needed. For example, when fungal, parasitic, or bacterial infections cause itching, topical or systemic drugs may be required. Topical drugs are applied directly to the affected area of the skin. Systemic drugs are taken by mouth or are injected and are distributed throughout the body.

Last full review/revision December 2006 by Peter C. Schalock, MD