R. Vender, MD, FRCPC
Division of Dermatology McMaster University, and Director of Dermatrials Research, Hamilton, Canada
Introduction
Itchy skin is a very common complaint seen in family practice as well as in dermatology practice. Causes of itchiness are extremely diverse and wide spread. A subset of nociceptive C neurons is responsible for the transmission of itch or pruritus, and these mediators (mainly histamine) can act centrally or peripherally. Skin disease that can mediate itchiness can originate in the skin or even in the central or peripheral nervous systems.
Dermatologic Diseases With Pruritus
| Dermatologic Disease | Cause |
| Infestation |
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| Inflammation |
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| Infections |
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| Neoplastic |
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| Hereditary or Congenital |
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| Others |
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Categories of Pruritus Therapy
| Causal therapy | Identification and treatment of the underlying disease |
| Symptomatic treatment |
|
Treatment of Specific Skin Disorders
Atopic Dermatitis
Moisturizing is extremely important for replenishing the skin’s water content and preventing water loss. Maintaining the barrier to keep out exacerbating factors from the skin, such as the external environment, is beneficial. Moisturizers should contain the following: emollients, humectants, occlusives, soothing agents and anti-irritants.
Oral antihistamines, especially those with sedating properties, e.g., hydroxyzine (Atarax®) or diphenhydramine (Benadryl®) may provide benefit for patients with pruritus. An antidepressant with potent antihistaminic properties, doxepin (Sinequan®), can also be useful. The role of histamine in eczema is questionable. Alpha hydroxy acids can reduce scaling and roughness.
Urticaria
Histamine release has a central role in urticaria. There are many causes of urticaria that can be investigated by an allergist. Oral antihistamines, either sedating or nonsedating, are beneficial. Nonsedating antihistamines, such as loratadine (Claritin®), desloratadine (Aerius®), or fexofenadine (Allegra®), can be used in combination with sedating antihistamines at bedtime.
Winter Itch
- The cold, dry air of Canadian winters increases transepidermal water loss and causes xerosis (severely dry skin).
- As we heat our homes, especially with electric heat, it reduces the humidity in the air.
- The skin tries to maintain an equilibrium, also causing an increase in transepidermal water loss.
- All ages can be affected.
- Can exacerbate underlying skin diseases associated with pruritus, which in turn can exacerbate pruritus further.
- Minimize soap. Nonsoap cleansers can be helpful (e.g., emulsifying ointment, Spectrogel®, Cetaphil®).
- Petrolatum depositing moisturizing body washes and in-shower moisturizers (e.g., Olay® Ribbons) can be helpful.
- Moisturizing after a bath is extremely important.
There is new evidence to show that moisturizers containing niacinamide and glycerin (e.g., Olay® Quench) not only hydrate the skin, but improve the skin’s resistance to external factors and improve the barrier function. Glycerin is required for moisturizers to work quickly and add moisture to the skin, but the niacinamide helps to sustain that benefit over a longer period of time.
Management
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Conclusion
The causes and differential diagnoses are as diverse for pruritus as the treatment and management are nonspecific. This makes the workup of nonspecific itch difficult. With careful history and physical exam, as well as some laboratory investigations, most serious disorders can be ruled out and the patient’s itch can be relieved.
