The Influence of Urea Treatment on Skin Susceptibility to Surfactant-Induced Irritation: A Placebo-Controlled and Randomized Study

Abstract

Certain ingredients in moisturizing creams may influence the skin susceptibility to irritants. One agent of particular interest is the well-known humectant urea. The present placebo-controlled study on 28 subjects was designed to evaluate the effects of urea treatment on three types of sodium lauryl sulphate (SLS) exposures: (1) repeated exposure to SLS for 15 days with concurrent cream treatment, (2) the skin susceptibility to SLS following prophylactic treatment with urea and (3) SLS exposure after recovery of the surfactant-damaged skin by urea treatment. Parameters measured were transepidermal water loss (TEWL) and skin blood flow. Repeated exposure to SLS induced a slight but significant barrier damage, measured as TEWL, and the difference between the treatments was almost significant (p = 0.06). Treatment of normal skin reduced TEWL in the urea-treated area, and the irritant reaction to SLS was significantly decreased. Treatment of surfactant-damaged skin promoted barrier recovery, and the second exposure to SLS induced a less pronounced reaction in the urea-treated area compared to the placebo-treated site. In conclusion, urea promotes barrier recovery in SLS-damaged skin and makes both normal and irritated skin less susceptible to irritation. The findings may be of clinical relevance in attempts to reduce contact dermatitis due to irritant stimuli.

Nickel Susceptibility and Skin Barrier Function to Water after Treatment with a Urea-Containing Moisturizer

“…These studies show that the irritant reaction after exposure to SLS is signifi cantly lower after urea treatment for 20 days than in the untreated skin [35,36] . This has also been confi rmed in a recent placebo-controlled study [37] . A decreased susceptibility to SLS was also found after 3 applications of both 5 and 10% urea moisturizers, although this decrease in susceptibility was not preceded by a reduction in TEWL [35] .…”

“…The cream in the present study contains urea, which previously has been found to improve skin barrier function to water and the irritant SLS [35][36][37] . Changes in the permeability barrier are suggested to be due to changes in the epidermal proliferation [18,19] and not to changes in the packaging of the barrier lipid matrix [61] .…”

The Use of Urea in the Treatment of Dry Skin

“…A decreased susceptibility to SLS was also noticed after three applications of both 5% and 10% urea moisturizers, although this decrease in susceptibility was not accompanied by a prior reduction in TEWL [ 80 ] . The improvement in skin barrier function has been confi rmed in a placebo-controlled study, where a significantly lower TEWL and reduced susceptibility to SLS were found in the urea-treated skin compared to the placebo-treated skin [ 83 ] . However, no change in skin reactivity to nickel in sensitized individuals was found after 3-week treatment with 5% urea [ 79 ] .…”

“…Reduced TEWL and reduced reactivity [ 83 ] Randomized, untreated control, blind evaluation (12) 10, cream 20 TEWL, SLS reactivity…”

“…In dry skin of environmental origin, no infl uence on TEWL was noted after treatment with a 3% urea cream, whereas TEWL decreased in skin treated with 10% urea cream [ 32 ] . In SLS-damaged skin, a 5% urea cream has been shown to promote barrier recovery, measured as TEWL [ 81,83 ] . Furthermore, in a placebo-controlled study, it has been shown that urea was responsible for the accelerated barrier recovery and decreased susceptibility to SLS [ 83 ] .…”