GDNF and Dry skin: Therefore, we assessed whether HDM extract could increase GDNF production by HaCaT and primary keratinocytes, and whether these increases could be suppressed by Aptamin C. As expected, HDM extract markedly increased the production of GDNF protein, an increase suppressed by treatment with Aptamin C. A cream containing Aptamin C has skin moisturizing effects and reduces itching in ordinary people with dry skin.