Introduction

Becoming proficient and knowledgeable about skin disease involves the accumulation of experience, but there are certainly pearls that can be shared to expedite the process. For example, even before one writes a single prescription for dermatitis, it is important to consider the patient’s bathing habits and overall skin care, because these habits and practices may have caused or perpetuated the skin problem.

Best Soaps for Xerosis and Dermatitis

Soaps are the most common irritant that people are exposed to each day, yet patients and providers do not always appreciate the differences among various soaps. Normal skin has a slightly acidic pH. The precise pH is site-dependent, but typically the skin pH is between 4.5 and 5.5. The skin has the ability to regulate pH, chiefly via production of lactic acid, with lactate contained in sebum (the so-called lipid mantle).

However, most soaps are lye-based and hence have a high pH in relation to the skin. For example, in one study, Neutrogena soap had a pH of 9.6, and Ivory soap had a pH of 10.1. Although there are other factors that affect the irritancy of a soap, in general, products with a neutral or slightly acidic pH are less irritating (e.g., Dove soap has a pH of 7.3; Cetaphil has a pH of 6.4).

As a general rule, lye-based and so-called natural soaps will often be more irritating than synthetic soaps (termed syndets [synesthetic detergents] in the soap industry). The composition of soaps may vary over time, and a brand name may have more than one line containing different components.

The box above lists common lye-based (natural) and synthetic soap ingredients (syndets). Patients do not need to know a long list of ingredients; they only need to know that the primary tensioactive agent of milder soaps has the word isethionate in the list of ingredients. All patients with xerosis, dermatitis, or recent dermatitis (within 4 weeks) may benefit from use of a syndet.

Gram-Negative Toe Web Infections: Another Soap Issue

Gram-negative toe web infections (GNTWIs) are common in humid climates and in persons with hyperhidrosis. GNTWIs often demonstrate an unpleasant odor and erythema, erosions, and purulence that may be yellow, yellow-green, or green-blue, especially if Pseudomonas is a dominant pathogen ( Fig. 37.1 ).

Severe pseudomonal toe web infection.

(From the William Weston Collection, Aurora, CO.)

Although prescription antimicrobial therapy is appropriate, a chief goal is to re-establish normal gram-positive commensals (GPCs). Military studies have indicated that use of antibacterial soaps preferentially deplete GPCs and could cause or worsen GNTWIs. This effect is not seen in those using soaps without certain antibacterial agents. Avoidance of over-the-counter (OTC) antibacterial soaps is an important step in the management of GNTWIs. Recently, the US Food and Drug Administration (FDA) asked manufacturers to cease use of 19 antibacterial ingredients in soap, including triclosan and triclocarban.