Du 毒 refers to something toxic, poisonous, venomous or narcotic. However, Yan Liu (2021) argues that the term used to refer to "potency" without the purely negative connotations that the words like "poison" or "toxicity" evoke today. Hence, a medicine like aconite may be listed as toxic but is still a valuable medicine in the doctors cabinet for it has the potency to attack an illness if used carefully while also retaining the power to harm if used incorrectly. The Shen Nong Ben Cao Jing used toxicity as its primary criteria for separating medicines into three tiers with the superior medicines used for enhancing life (Yangsheng) being non-toxic and permissible to take continuously, the middle group being sometimes toxic and suitable for strengthening the body and preventing disease, while the lowest tier were the toxic drugs used to attack illness and cure disease. This also means diseases classed as "toxic" (usually epidemics and skin diseases) really mean "severe" and that herbs with the action to resolve toxicity have the capacity to reduce the severity of an illness or the harsh actions of potent herbs and are not expelling or transforming an actual toxic substance as is generally understood in western detox culture. Substances aimed at expelling were usually listed as toxic themselves, applying the principle of "using poison to attack poison".
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