My favorite bit of folk medicine is that we’re supposed to take wormwood for intestinal parasites. It’s actually really effective, which is how wormwood got its name, but the reason it’s effective is that wormwood is literally just poison and it happens to kill the worms slightly faster than it kills you.
That’s medicine BABEYYYYYY!!!!
No, but seriously, the reason plants have useful chemicals that we can use medicinally is because they have evolved those chemicals as poisons to prevent predation. Humans were just smart enough to figure out through trial and error how to balance these chemical extracts to counteract abnormalities in our bodies.
Like: “Hm. This plant toxin is a cardiac glycoside and increases heart output. In a healthy person, this is highly unpleasant and may even cause death. But… for my aging aunt over here who’s suffering from congestive heart failure… a little foxglove extract taken every morning with her tea would probably help her circulation and keep her weary heart kickin’ for a few more years.”
Medicine is the opportune application of poisons. Healers and poisoners are folks with similar skill sets and wildly different philosophies.
Speaking as a healer, conventional and metaphysical, you have to know what kills in order to know how to fix it.