'The roots of Hemerocallis species (day lilies) ingested by goats, sheep and cattle, and used for the treatment of schisotosomiasis in humans, have caused fatalities in the People's Republic of China'. Active principle is hemerocallin (stypandrol),

In traditional medicine, The flower of the related species H. fulva is said to deaden pain, given in childbirth. The root of the same species has a folk history of use in the treatment of cancer - extracts from the roots have shown antitumour activity.

see ref (in full under toxicity)

Hemerocallis species have caused fatalities in the People's Republic of China, when taken for treating schistosomiasis. Active principle of H. thunbergii isolated from the roots, is hemerocallin, which has the same structure, clinical and pathological effects as stypandrol (from Stypendra imbriciata - called Blind Grass - producing mydriasis, progressive and irreversible blindness and paralysis. Hemerocallis esculenta, H. altissima, H. lilio-asphodelus and H. minor are also toxic. The same chemical is found in the leaves of Dianella revoluta (blue-flax lily).

The flower of the related species H. fulva has been used in traditional medicine to deaden pain in childbirth and the root of the same species has a folk history of use in the treatment of cancer - extracts from the roots have shown antitumour activity.