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Am Fam Physician. 2012;85(9):online

Original Article: A Diagnostic Approach to Pruritus

Issue Date: July 15, 2011

to the editor: Drs. Reamy, Bunt, and Fletcher give a thorough and medically traditional review of the diagnostic approach to pruritus in primary care. However, what I found lacking are some common-sense diagnoses I find far more frequently in primary care practice than those described in the article and in the medical literature.

With 36 years of family medicine experience, I have found the most common cause of pruritus is soap. I am convinced that in the United States, soap causes more people to go to the doctor than the lack of it. Soap takes the natural oils out of the skin, causing itching. Some people shower or bathe two to three times a day and soap their entire body. Although soap is fine for the heavy sweat areas such as the face, axilla, and groin, soap dries out the arms, trunk, and legs. When I see patients who have itching and no rash, I ask how often they bathe and how they use soap. The answers are surprising, and the patients often think that itching skin is dirty and needs more soap.

In my California practice, I see an epidemic of dry skin dermatitis and itching every January. That is because people tend to shower or bathe with the same routine all year, yet in the winter their skin sweats very little, and soap dries them out.

Anal itching is a common problem. Again, soap is often the culprit.1 In adults, anal itching with a dermatitis reaction around the anus is usually caused by using moist towlettes containing a type of soap.

The authors do list xerosis (dry skin) among the etiologies for pruritus, but without the emphasis it deserves, especially its relationship to the use of soap. Looking for common-sense causes of pruritus first, and more serious medical etiologies second, has served me well in family medicine, and has allowed me to help most patients without an expensive workup.

to the editor: I admired this article but was surprised that no mention was made of the use of doxepin in treating pruritus. Doxepin has more potent histamine H1 receptor antagonist properties than either diphenhydramine or hydroxyzine1 and has been found to be a more effective antipruritic agent than diphenhydramine for chronic urticaria.2

in reply: We appreciate Dr. Scherger's letter, which reinforces several points we made in our article on pruritus. As we stated, xerosis is the most common cause of pruritus in the absence of an identifiable skin lesion. It is characterized by dry, scaly skin, and most often occurs in winter. Xerosis is exacerbated by overly frequent bathing, especially bathing with hot water.

The algorithm we presented in Figure 1 clearly states that when history and physical examination suggest an underlying diagnosis, no laboratory or other testing is suggested. The appearance of dry, flaky skin with a concurrent history of excessive bathing during the winter easily lends itself to a diagnosis of xerosis, and no further testing is indicated. Appropriate treatment would include removing the irritants (drying soaps, excessive bathing) and applying moisturizing lotions or creams.

Dr. Blum points out that the tricyclic antidepressant doxepin can be used off-label as an effective antipruritic agent for chronic urticaria. We agree that this is a possible treatment option, but its potent sedativehypnotic side effects can be problematic in some patients.

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This series is coordinated by Kenny Lin, MD, MPH, deputy editor.

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