In many cases the plant substances are highly toxic
Administering them is dosages high enough to be effective may do more harm than the original infection
The FDA does not approve supplements.
“Consumer Reports” (Jan. 2023) had a review of supplements and it listed these supplements to always avoid. Many cause serious harm:
Chaparral (creasote bush, greasewood, Larrea divaricata, Larrea tridentata, larreastat): Kidney problems, liver damage.
Coltsfoot (coughwort, Farfarae folium leaf, foalswort, Tussilago farfara): Liver damage, possible carcinogen.
Comfrey (blackwort, bruisewort, slippery root, Symphytum officinale): Liver damage, cancer.
Germander (Teucrium chamaedrys, Teucrium viscidum): Liver damage, hepatitis.
Greater Celandine (celandine, Chelidonium majus): Liver damage.
Kava (ava pepper, kava kava, Piper methysticum): Liver damage, exacerbates Parkinson’s disease and depression, impairs driving.
Lobelia (asthma weed, Lobelia inflata,vomit wort, wild tobacco): nausea, vomiting, kiarrhea, tremors, rapid heartbeat, confusion, seizures, hypothermia, coma.
Pennyroyal Oil (Hedeoma puleggiodes, Mentha pulegium): Liver and kidney failure, nerve damage, convulsions.
Usnic Acid (beard moss, tree moss, usnea): Liver injury.
Yohimbe (Johimbi, Pausinystalia yohimbe, yohimbine, Corynanthe johimbi): raises blood pressure, causes rapid heart rate, headaches, seizures, liver and kidney problems, heart problems, panic attacks.