Many books on herbs use terms such as poisonous (youdu 
), extremely poisonous (dadu 
), slightly poisonous (xiaodu 
) and non-poisonous (wudu 
). What actually is meant by the toxicity of Chinese medicines? Why are Chinese medicines poisonous, and why are “extremely poisonous” medicines still in use?
Ancient and modern definitions of poison (du 
)
The ancient Chinese definition of a medicine’s poison (du 
) refers to the tendency of the medicine’s effects. It explains the extent of its toxic side effects. The curative principle of Chinese medicines is “rectifying tendency with tendency” (yi pian jiu pian 
).Shen Nong’s Herbal Classic mentions combating poison with poison (yi du gong du 
). Thus the terms extremely poisonous (dadu 
), poisonous (youdu 
) and slightly poisonous (xiaodu 
) are usually referred to as the extent of the poison’s side effects.
Today, people perceive the poisonous qualities of medicine as causing severe damages to living organisms, with disastrous outcome such as cancer, mutation, deformity, and addiction. The modern-day concept of Chinese medicines’ side effects, however, refers to the adverse reactions that result from the regular dosage intake during treatment. It does not cause much harm to the body and symptoms will cease once medication stops.
How to determine whether a medicinal material is poisonous
1. Does it have a toxic component?
According to modern medical research, whether or not a medicinal material is poisonous depends on whether any of its components are toxic. For instance, mesaconitine is poisonous due to its chemical components of aconitine, hypaconitine, etc.
2. Is the entire material poisonous?
While all poisonous materials will have toxic components, not all materials that have toxic components will be poisonous. This is because of the antagonistic relationship between the components of certain Chinese medicinal materials. For instance, certain constituents of ginseng thicken the blood while others dilute it, and they negate each others’ effects.
3. Is the dosage suitable?
If a Chinese medicine is taken in the correct dosage, it will be harmless to the body and therefore considered non-toxic. If an overdose is taken, however, it will have toxic side effects and be considered poisonous.