Pig skin arch refers to the fishy grass, generally known as pig skin arch in Sichuan.

Fishy grass is a herb listed in the Chinese Pharmacopoeia, the source of the herb is the dried above-ground part of Houttuynia cordata, family Houttuyniaceae. It is harvested in summer when the stems and leaves are lush with many flower spikes, and the impurities are removed and dried in the sun.