Fresh walnut green peel is poisonous, and its juice may cause allergies, but it can be used as medicine after drying and is beneficial to the human body.

Walnut green peel: also known as green walnut peel or green longyi, it is the outer peel of the immature fruit of walnut, a plant in the Juglandaceae family. Harvest immature fruits in autumn, dry them in the sun until the outer skin cracks, pick out the outer peel, and then dry it in the sun to contain oxidized walnut leaf quinone. According to the "Shandong Chinese Herbal Medicine Manual", the green skin of walnuts is bitter and flat (poisonous). It is mainly used to treat stomach and abdominal pain, water dysentery, carbuncle sores, psoriasis, ichthyosis, ringworm and baldness.