Itching

Definition

Itching is an intense, distracting irritation or tickling sensation that may be felt all over the skin's surface, or confined to just one area. The medical term for itching is pruritus.

Description

Itching instinctively leads most people to scratch the affected area. Different people can tolerate different amounts of itching, and anyone's threshold of tolerance can be changed due to stress, emotions, and other factors. In general, itching is more severe if the skin is warm, and if there are few distractions. This is why people tend to notice itching more at night.

Causes and symptoms

The biology underlying itching is not fully understood. It is believed that itching results from the interactions of several different chemical messengers. Although itching and pain sensations were at one time thought to be sent along the same nerve pathways, researchers reported the discovery in 2003 of itch-specific nerve pathways. Nerve endings that are specifically sensitive to itching have been named pruriceptors.

Research into itching has been helped by the recent invention of a mechanical device called the Matcher, which electrically stimulates the patient's left hand. When the intensity of the stimulation equals the intensity of itching that the patient is experiencing elsewhere in the body, the patient stops the stimulation and the device automatically records the measurement. The Matcher was found to be sensitive to immediate changes in the patient's perception of itching as well as reliable in its measurements.

Stress and emotional upset can make itching worse, no matter what the underlying cause. If emotional problems are the primary reason for the itch, the condition is known as psychogenic itching. Some people become convinced that their itch is caused by a parasite; this conviction is often linked to burning sensations in the tongue, and may be caused by a major psychiatric disorder.

Generalized itching

Itching that occurs all over the body may indicate a medical condition such as diabetes mellitus, liver disease, kidney failure, jaundice, thyroid disorders (and rarely, cancer). Blood disorders such as leukemia, and lymphatic conditions such as Hodgkin's disease may sometimes cause itching as well.

Some people may develop an itch without a rash when they take certain drugs (such as aspirin, codeine, cocaine); others may develop an itchy red "drug rash" or hives because of an allergy to a specific drug. Some medications given to cancer patients may also cause itching.

Itching also may be caused when any of the family of hookworm larvae penetrate the skin. This includes swimmer's itch and creeping eruption caused by cat or dog hookworm, and ground itch caused by the "true" hookworm.

Many skin conditions cause an itchy rash. These include:

• Atopic dermatitis
  
• Chickenpox
  
• Contact dermatitis
  
• Dermatitis herpetiformis (occasionally)
  
• Eczema
  
• Fungus infections (such as athlete's foot)
  
• Hives (urticaria)
  
• Insect bites
  
• Lice
  
• Lichen planus
  
• Neurodermatitis (lichen simplex chronicus)
  
• Psoriasis (occasionally)
  
• Scabies.
  

On the other hand, itching all over the body can be caused by something as simple as bathing too often, which removes the skin's natural oils and may make the skin too dry and scaly.

Localized itching

Specific itchy areas may occur if a person comes in contact with soap, detergents, and wool or other rough-textured, scratchy material. Adults who have hemorrhoids, anal fissure, or persistent diarrhea may notice itching around the anus (called "pruritus ani"). In children, itching in this area is most likely due to worms.

Intense itching in the external genitalia in women ("pruritus vulvae") may be due to candidiasis, hormonal changes, or the use of certain spermicides or vaginal suppositories, ointments, or deodorants.

It is also common for older people to suffer from dry, itchy skin (especially on the back) for no obvious reason. Younger people also may notice dry, itchy skin in cold weather. Itching is also a common complaint during pregnancy.

Diagnosis

Itching is a symptom that is quite obvious to its victim. Someone who itches all over should seek medical care. Because itching can be caused by such a wide variety of triggers, a complete physical exam and medical history will help diagnose the underlying problem. A variety of blood and stool tests may help determine the underlying cause.

Treatment

Antihistamines such as diphenhydramine (Benadryl) can help relieve itching caused by hives, but will not affect itching from other causes. Most antihistamines also make people sleepy, which can help patients sleep who would otherwise be awake from the itch.

Specific treatment of itching depends on the underlying condition that causes it. In general, itchy skin should be treated very gently. While scratching may temporarily ease the itch, in the long run scratching just makes it worse. In addition, scratching can lead to an endless cycle of itch-scratch-more itching.

To avoid the urge to scratch, a person can apply a cooling or soothing lotion or cold compress when the urge to scratch occurs. Soaps are often irritating to the skin, and can make an itch worse; they should be avoided, or used only when necessary.

Creams or ointments containing cortisone may help control the itch from insect bites, contact dermatitis or eczema. Cortisone cream should not be applied to the face unless a doctor prescribes it.

Probably the most common cause of itching is dry skin. There are a number of simple things a person can do to ease the annoying itch:

• Do not wear tight clothes
  
• Avoid synthetic fabrics
  
• Do not take long baths
  
• Wash the area in lukewarm water with a little baking soda
  
• For generalized itching, take a lukewarm shower
  
• Try a lukewarm oatmeal (or Aveeno) bath for generalized itching
  
• Apply bath oil or lotion (without added colors or scents) right after bathing.
  

Itching may also be treated with whole-body medications. In addition to antihistamines, some of these systemic treatments include:

• tricyclic antidepressants
  
• sedatives or tranquilizers
  
• such selective serotonin reputake inhibitors as paroxetine (Paxil) and sertraline (Zoloft)
  
• binding agents (such as cholestyramine which relieves itching associated with kidney or liver disease).
  
• aspirin
  
• cimetidine
  

People who itch as a result of mental problems or stress should seek help from a mental health expert.

Alternative and complementary therapies

A well-balanced diet that includes carbohydrates, fats, minerals, proteins, vitamins, and liquids will help to maintain skin health. Capsules that contain eicosapentaenoic acid, which is obtained from herring, mackerel, or salmon, may help to reduce itching. Vitamin A plays an important role in skin health. Vitamin E (capsules or ointment) may reduce itching. Patients should check with their treating physician before using supplements.

Homeopathy has been reported to be effective in treating systemic itching associated with hemodialysis.

Baths containing oil with milk or oatmeal are effective at relieving localized itching. Evening primrose oil may soothe itching and may be as effective as corticosteroids. Calendula cream may relieve short-term itching. Other herbal treatments that have been recently reported to relieve itching include sangre de drago, a preparation made with sap from a South American tree; and a mixture of honey, olive oil, and beeswax.

Distraction, music therapy, relaxation techniques, and visualization may be useful in relieving itching. Ultraviolet light therapy may relieve itching associated with conditions of the skin, kidneys, blood, and gallbladder. There are some reports of the use of acupuncture and transcutaneous electrical nerve stimulators (TENS) to relieve itching.

Prognosis

Most cases of itching go away when the underlying cause is treated successfully.

Prevention

There are certain things people can do to avoid itchy skin. Patients who tend toward itchy skin should:

• Avoid a daily bath
  
• Use only lukewarm water when bathing
  
• Use only gentle soap
  
• Pat dry, not rub dry, after bathing, leaving a bit of water on the skin
  
• Apply a moisture-holding ointment or cream after the bath
  
• Use a humidifier in the home.
  

Patients who are allergic to certain substances, medications, and so on can avoid the resulting itch if they avoid contact with the allergen. Avoiding insect bites, bee stings, poison ivy and so on can prevent the resulting itch. Treating sensitive skin carefully, avoiding overdrying of the skin, and protecting against diseases that cause itchy rashes are all good ways to avoid itching.

Key Terms

Atopic dermatitis: An intensely itchy inflammation often found on the face of people prone to allergies. In infants and early childhood, it is called infantile eczema.

Creeping eruption: Itchy irregular, wandering red lines on the foot made by burrowing larvae of the hookworm family and some roundworms.

Dermatitis herpetiformis: A chronic very itchy skin disease with groups of red lesions that leave spots behind when they heal. It is sometimes associated with cancer of an internal organ.

Eczema: A superficial type of inflammation of the skin that may be very itchy and weeping in the early stages; later, the affected skin becomes crusted, scaly, and thick. There is no known cause.

Hodgkin's disease: A type of cancer characterized by a slowly-enlarging lymph tissue; symptoms include generalized itching.

Lichen planus: A noncancerous, chronic itchy skin disease that causes small, flat purple plaques on wrists, forearm, ankles.

Neurodermatitis: An itchy skin disease (also called lichen simplex chronicus) found in nervous, anxious people.

Pruriceptors: Nerve endings specialized to perceive itching sensations.

Pruritus: The medical term for itching.

Psoriasis: A common, chronic skin disorder that causes red patches anywhere on the body. Occasionally, the lesions may itch.

Scabies: A contagious parasitic skin disease characterized by intense itching.

Swimmer's itch: An allergic skin inflammation caused by a sensitivity to flatworms that die under the skin, causing an itchy rash.

Resources

Books

• Beers, Mark H., MD, and Robert Berkow, MD, editors. "Pruritus." Section 10, Chapter 109. In The Merck Manual of Diagnosis and Therapy. Whitehouse Station, NJ: Merck Research Laboratories, 2004.
  

Periodicals

• Al-Waili, N. S. "Topical Application of Natural Honey, Beeswax and Olive Oil Mixture for Atopic Dermatitis or Psoriasis: Partially Controlled, Single-Blinded Study." Complementary Therapies in Medicine 11 (December 2003): 226-234.
  
• Browning, J., B. Combes, and M. J. Mayo. "Long-Term Efficacy of Sertraline as a Treatment for Cholestatic Pruritus in Patients with Primary Biliary Cirrhosis." American Journal of Gastroenterology 98 (December 2003): 2736-2741.
  
• Cavalcanti, A. M., L. M. Rocha, R. Carillo Jr., et al. "Effects of Homeopathic Treatment on Pruritus of Haemodialysis Patients: A Randomised Placebo-Controlled Double-Blind Trial." Homeopathy 92 (October 2003): 177-181.
  
• Ikoma, A., R. Rukwied, S. Stander, et al. "Neurophysiology of Pruritus: Interaction of Itch and Pain." Archives of Dermatology 139 (November 2003): 1475-1478.
  
• Jones, K. "Review of Sangre de Drago (Croton lechleri)-A South American Tree Sap in the Treatment of Diarrhea, Inflammation, Insect Bites, Viral Infections, and Wounds: Traditional Uses to Clinical Research." Journal of Alternative and Complementary Medicine 9 (December 2003): 877-896.
  
• Ochoa, J. G. "Pruritus, a Rare but Troublesome Adverse Reaction of Topiramate." Seizure 12 (October 2003): 516-518.
  
• Stener-Victorin, E., T. Lundeberg, J. Kowalski, et al. "Perceptual Matching for Assessment of Itch; Reliability and Responsiveness Analyzed by a Rank-Invariant Statistical Method." Journal of Investigative Dermatology 121 (December 2003): 1301-1305.
  
• Zylicz, Z., M. Krajnik, A. A. Sorge, and M. Costantini. "Paroxetine in the Treatment of Severe Non-Dermatological Pruritus: A Randomized, Controlled Trial." Journal of Pain and Symptom Management 26 (December 2003): 1105-1112.

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Source: Gale Encyclopedia of Medicine, Published December, 2002 by the Gale Group. The Essay Author is Carol A. Turkington.

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