http://www.cdc.gov/ncidod/eid/vol7no2/larson.htm Water content, humidity, pH, intracellular lipids, and rates of shedding help retain the protective barrier properties of the skin. When the barrier is compromised (e.g., by hand hygiene practices such as scrubbing), skin dryness, irritation, cracking, and other problems may result. Although the palmar surface of the hand has twice as many cell layers and the cells are >30 times thicker than on the rest of the skin (47), palms are quite permeable to water (48).
Long-term changes in skin pH associated with handwashing may pose a concern since some of the antibacterial characteristics of skin are associated with its normally acidic pH (49). In one report, pH increased 0.6 to 1.8 units after handwashing with plain soap for 1 to 2 min and then gradually declined to baseline levels over a period of 45 min to 2 hr (50). Some soaps can be associated with long-standing changes in skin pH, reduction in fatty acids, and subsequent changes in resident flora such as propionibacter (51).
In an investigation of the effect on skin of repeated use of two washing agents, all skin function tests (stratum corneum capacitative resistance, lipids, transepidermal water loss, pH, laser Doppler flow, and skin reddening) were markedly changed after a single wash, and after 1 week further damage was noted (52). In a study of irritant skin reactions induced by three surfactants, damage lasted for several days; complete skin repair was not achieved for 17 days (53).
Soaps and detergents have been described as the most damaging of all substances routinely applied to skin (43). Anionic and cationic detergents are more harmful than nonionic detergents (54), and increased concentrations of surfactant result in more rapid, severe damage (55). Each time the skin is washed, it undergoes profound changes, most of them transient. However, among persons in occupations such as health care in which frequent handwashing is required, long-term changes in the skin can result in chronic damage, irritant contact dermatitis and eczema, and concomitant changes in flora.