Inhibitory Effect of Polyphenol-Rich Fraction from the Bark of Acacia mearnsii on Itching Associated with Allergic Dermatitis

We examined the inhibitory effect of polyphenol-rich aqueous extract from the bark of Acacia mearnsii (PrA) on itching associated with atopic dermatitis (AD). HR-1 mice were fed a normal diet, special diet (AD group), or special diet containing 3% PrA (PrA group) for 6 weeks. In the AD group, itching frequency and transepidermal water loss increased compared to the control group. In the PrA group, an improvement in atopic dermatitis symptoms was observed. Ceramide expression in the skin decreased in the AD group compared to the control group, but no decrease was observed in the PrA group. mRNA expression of ceramidase decreased in the PrA group compared to the AD group. The results of this study have revealed that PrA inhibits itching in atopic dermatitis by preventing the skin from drying. It is considered that the mechanism by which PrA prevents the skin from drying involves the inhibition of increased ceramidase expression associated with atopic dermatitis.