Topical N-acetylcysteine can restore skin barrier function in healthy volunteers and atopic dermatitis patients

Atopic dermatitis (AD) is a relapsing chronic inflammatory pruritic skin disorder that has been partially attributed to skin barrier dysfunction. Skin barrier function has previously been estimated by measuring skin hydration and transepidermal water loss (TEWL), and low levels of skin hydration and high levels of TEWL have been reported in AD patients. N-acetylcysteine (NAC) is a thiol derivative that stimulates the synthesis of glutathione, an internal antioxidant. Previous studies reported that NAC was useful for treating skin diseases such as toxic epidermal necrolysis and lamellar ichthyosis. In the present study, we assessed the clinical effects of topical NAC on skin hydration and TEWL in healthy volunteers and AD patients. Ten healthy volunteers and 11 AD patients were enrolled. NAC solution (20 w/v%) or its control vehicle was applied to the skin of the forearm twice a day for 4 weeks. Skin hydration and TEWL in the forearm were measured before and after the topical application of NAC solution. The topical application of NAC for 4 weeks increased skin hydration in 9/10 healthy volunteers and decreased TEWL in 8/10 healthy volunteers. Topical application of the control vehicle for 4 weeks decreased skin hydration in 8/11 AD patients. The topical application of NAC increased skin hydration in 9/11 AD patients and decreased TEWL in 9 AD patients. Recently, we have reported that NAC restored the expression of some cell adhesion molecules that contribute to forming the skin barrier in a mouse model of AD by reducing oxidative stress. Therefore, the topical application of NAC may have increased skin hydration and decreased TEWL by strengthening the function of this barrier. Our results may also support the possibility of NAC restoring skin barrier function.