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Itching

by Karen McKoy, MD, MPH

Itching can be very uncomfortable. It is one of the most common reasons people see dermatologists. Itching can be triggered by wool fibers or irritants, such as solvents or cosmetics.

Itching can result from disorders that affect the skin, the nervous system (which senses itching), or other parts of the body (such as bile ducts or kidneys) or from drugs. Causes that affect more of the body than just the skin are called systemic causes.

Itching makes people want to scratch. Scratching temporarily relieves itching but can damage the skin, sometimes resulting in more itching or infection. Over time, the skin can become thick and scaly.

Causes

The most common causes of itching are related to skin disorders:

  • Dry skin

  • Eczema (also called atopic dermatitis)

  • Contact dermatitis (an allergic rash resulting from direct contact with a particular substance)

  • Fungal skin infections

Systemic causes are less common but are more likely if there is no visible skin problem. Some of the more common systemic causes are

  • Allergic reactions that have internal effects—for example, to foods, drugs, bites, or stings (internal allergic reactions)

  • Disorders of the gallbladder or liver, such as gallstones

  • Chronic kidney disease

Less common systemic causes include an overactive thyroid gland (hyperthyroidism), an underactive thyroid gland (hypothyroidism), diabetes, iron deficiency, and polycythemia vera (a cancerous overproduction of red blood cells). Drugs can cause itching by causing allergic reactions. Drugs can also cause itching without causing an allergic reaction. For example, morphine and some radiopaque dyes given by vein (intravenously) may cause itching.

Evaluation

Not every episode of itching requires immediate evaluation by a doctor. The following information can help people decide whether a doctor's evaluation is needed and help them know what to expect during the evaluation. Most conditions causing itching are not serious.

Warning signs

The following may indicate that the cause could be serious:

  • Weight loss, fatigue, or night sweats—symptoms that may indicate a serious infection or a tumor

  • Weakness, numbness, or tingling—symptoms that may indicate a nervous system disorder

  • Abdominal pain or a yellowish discoloration of the skin and eyes (jaundice)—symptoms that may indicate a gallbladder or liver disorder

  • Excessive thirst, abnormally frequent urination, and weight loss—symptoms that may indicate diabetes

When to see a doctor

People who have weight loss, fatigue, or night sweats should see a doctor as soon as convenient, probably within a week or so. People with any of the other warning signs or with severe itching should probably see a doctor immediately or as soon as possible.

What the doctor does

Doctors ask many questions and look at the skin. Often, a person needs to undress so that the entire skin surface can be checked. If no clear cause is found after checking the skin, doctors may do a complete physical examination to check for systemic causes. Testing may be necessary to diagnose certain systemic causes and sometimes skin disorders.

If itching is widespread and begins shortly after use of a drug, that drug is a likely cause. If itching (usually with a rash) is confined to an area in contact with a substance, particularly if the substance is known to cause contact dermatitis, that substance is a likely cause. However, allergic causes of widespread itching can be difficult to identify because affected people have usually eaten several different foods and have been exposed to many substances that could cause an allergic reaction before itching develops. Similarly, identifying a drug that is causing the reaction in a person taking several drugs may be difficult. Sometimes the person has been taking the drug causing the reaction for months or even years before a reaction occurs.

Some Causes and Features of Itching

Cause

Common Features*

Tests

Skin causes

Contact dermatitis

Redness and sometimes blisters in a shape or location corresponding to the substance causing the reaction (such as along the hairline when caused by hair dyes, on the wrist when caused by a watch, or on exposed skin when caused by poison ivy)

A doctor's examination

Dry skin

Dry, scaly skin, usually on the legs, that develops or becomes worse in winter, after a hot bath, or after prolonged exposure to water

A doctor's examination

Eczema (atopic dermatitis)

Dryness, redness, and sometimes thickening and scaling, often in the folds of the elbows or behind the knees

Usually a family history of allergies or rashes

A doctor's examination

Fungal skin infections, such as ringworm, jock itch, or athlete's foot

A circular rash with raised borders, scaling, and often hair loss

In adults, usually on the feet or genital area

In children, usually on the scalp or body

Sometimes examination of skin scales under a microscope

Hives (urticaria)

Red, raised swellings that have sharp borders and are often clear in the center

Each hive resolving within hours, but new hives continuing to appear, sometimes repeatedly

Usually only a doctor's examination

Insect bite

Sudden appearance of one or a few bumps that are usually small, red, and raised

A doctor's examination

Lice infestation (pediculosis)

Areas of scratched, irritated skin and sometimes tiny, pinpoint bites

Usually in the scalp, armpits, or pubic area or on the waist or eyelashes

Sometimes examination of skin scales or debris under a microscope

Lichen simplex chronicus

Areas where repeatedly scratched skin has thickened

Areas are red, scaly, raised, rough, and separated from surrounding skin

A doctor's examination

Psoriasis

Raised red patches with silver scales

Usually on the outer exposed surface of the elbows or knees or on the scalp or trunk

A doctor's examination

Scabies

Burrows, which are small red or dark bumps, next to a fine, wavy, slightly scaly short line

Usually in the web spaces between the fingers or toes, along the belt (waist) line, on the inner surfaces of the elbows, behind the knees, around the nipples (in women), or near the genitals (in men)

Sometimes examination of skin scales or debris under a microscope

Systemic causes (conditions that affect more of the body than just the skin)

Allergic reactions that have internal effects

Widespread itching

Often a raised red rash and sometimes hives

Avoiding things one at a time to see what the cause is

Sometimes skin testing

Cancer, such as Hodgkin lymphoma, certain other lymphomas such as mycosis fungoides, and polycythemia vera

Itching sometimes as the first symptom of cancer

With Hodgkin lymphoma, burning with itching, particularly in the legs

With mycosis fungoides, various raised or flat skin patches or reddening of the skin

With polycythemia vera, itching without a rash

A complete blood count

A chest x-ray

A biopsy of lymph nodes for Hodgkin lymphoma, of skin for mycosis fungoides, or of bone marrow for polycythemia vera

Chronic kidney disease

Widespread itching and no rash

Sometimes worse during dialysis and sometimes worse on the back

Tests to exclude other causes of itching, based on the person's symptoms

Diabetes

Frequent urination, thirst, and weight loss

Itching usually occurring only after other symptoms have developed

Blood tests for level of sugar (glucose) and glycosylated hemoglobin (which indicates the level of blood sugar over time)

Drugs, such as aspirin, barbiturates, cocaine, morphine, penicillin, and some antifungal and chemotherapy drugs

Sometimes no rash

A doctor's examination

Gallbladder or liver disorders

Other symptoms of gallbladder or liver disorders, such as jaundice, fatigue, oily stools, and abdominal pain

Usually blood tests to measure liver enzymes and ultrasonography

Iron deficiency anemia

Tendency to tire easily

Sometimes paleness, weakness, or difficulty breathing

Blood tests for anemia and iron deficiency

Multiple sclerosis

Intense itching that comes and goes

Other symptoms of multiple sclerosis, such as numbness and tingling, weakness, loss of vision, vertigo, and clumsiness

Magnetic resonance imaging (MRI) of the brain, spinal cord, or both

Sometimes a spinal tap

Sometimes electroencephalography or electromyography

Pregnancy

Usually widespread itching without rash, developing sometimes in late pregnancy

Sometimes resulting from mild liver problems

Sometimes blood tests to check for a liver disorder

Psychologic factors

Linear skin scratches and/or scabs in different stages of healing, and psychologic symptoms

Tests to exclude other causes of itching, based on the person's symptoms

Thyroid disorders

With hyperthyroidism (an overactive thyroid gland): Difficulty tolerating heat, sweating, weight loss, bulging eyes, shakiness (tremor), restlessness, and sometimes an enlarged thyroid gland (goiter)

With hypothyroidism (an underactive thyroid gland): Difficulty tolerating cold, weight gain, coarse and thick skin, and sluggishness

Blood tests to evaluate thyroid function

*Features include symptoms and results of the doctor's examination. Features mentioned are typical but not always present.

Testing

Most causes of itching can be diagnosed without testing. If the diagnosis of a skin abnormality is not clear from its appearance and the person's history, removal (biopsy) of a skin sample may be necessary so that it can be analyzed. If the cause of itching seems to be an allergic reaction but the substance causing the allergic reaction is not evident, skin testing may be necessary. In skin testing, substances that can cause allergic reactions on contact are applied to the skin, either in a patch (called patch testing) or with a small needle (called prick testing).

If the cause seems not be an allergic reaction or skin disorder, testing is done based on the person's other symptoms. For example, tests may be done for gallbladder or liver disorders, chronic kidney disease, thyroid disorders, diabetes, or cancer.

Treatment

Disorders that cause itching are treated. Sometimes other measures can also help relieve itching.

Skin care

Skin care measures can help relieve itching regardless of cause. Baths or showers should be short, no more frequent than necessary, and taken with cool or lukewarm (not hot) water. Using moisturizing soap and skin lubricants can also help, as can humidifying dry air (for example, in winter) and not wearing tight or wool clothing.

Topical treatments

Topical treatments can be applied to the skin if only a specific area is affected. To be effective, capsaicin cream should be used for at least 2 weeks. It tends to burn, but the burning decreases over time. Menthol and camphor creams have strong odors but can be used, as can tacrolimus or pimecrolimus creams.

Corticosteroid creams can help relieve itching and often clear up the rash and other skin abnormalities in disorders such as eczema, contact dermatitis, psoriasis, and lichen simplex chronicus. Corticosteroids should usually not be used when the skin is infected, when an infestation is present, when no rash or skin abnormalities are present, and when the cause is systemic.

Type B ultraviolet light can relieve itching but can cause sunburn-like effects and increases the risk of skin cancers.

Systemic treatments

Systemic treatments are drugs that are taken internally, usually by mouth. They are used if itching is widespread or if topical treatments are ineffective.

Antihistamines, particularly hydroxyzine, are used most often. Some antihistamines, such as cyproheptadine, diphenhydramine, and hydroxyzine, cause drowsiness. They help relieve itching and, when used before bedtime, aid in sleep. However, these drugs are usually not given during the day to older people, who are at higher risk of falling because of drowsiness. Cetirizine and loratadine cause less drowsiness but rarely can have this effect in older people. Fexofenadine causes less drowsiness but sometimes causes a headache. Doxepin makes people very drowsy and is effective, so it can be taken at bedtime if itching is severe.

Cholestyramine is used to treat itching caused by gallbladder or liver disorders, chronic kidney disease, or polycythemia vera. However, cholestyramine has an unpleasant taste, causes constipation, and can decrease absorption of other drugs. Naltrexone can be used to treat itching caused by gallbladder or liver disorders but may increase pain if pain is present. Gabapentin can help relieve itching caused by chronic kidney disease but can cause drowsiness.

Key Points

  • Itching usually results from dry skin, a skin disorder, or an allergic reaction.

  • If the person has no rash or skin abnormalities, the cause may be a drug, an allergic reaction that has internal effects, or a systemic disorder.

  • Skin care measures (such as limiting bathing, moisturizing the skin, and humidifying the air) can usually help relieve itching.

  • Itching can usually be relieved by topical or systemic treatments.

Resources In This Article

Drugs Mentioned In This Article

  • Generic Name
    Select Brand Names
  • DURAMORPH PF, MS CONTIN
  • No US brand name
  • QUTENZA
  • ELIDEL
  • PROGRAF
  • NEURONTIN
  • ALLEGRA
  • REVIA
  • VISTARIL
  • ZONALON
  • ZYRTEC
  • ALAVERT, CLARITIN