Medicinal plants: remedy or poison?

Natural doesn’t mean harmless.

Just as the therapeutic power of some medicinal plants is often underestimated, so too are their potential contraindications, interactions, and toxic effects often overlooked.

There are plants that are notoriously toxic such as:

– Hemlock (the lethal dose for humans is a few grams of green fruits).

– Aconite (all parts of the plant contain toxic alkaloids, with the highest concentration found in the root. It can cause fatal poisoning leading to respiratory arrest).

Species belonging to the Colchicum genus, very common in Italy.

The most well-known species is Colchicum autumnale, which in folk medicine, in very low doses, was used as an analgesic, antipyretic, and antitumor agent.

The plant is considered poisonous because it contains colchicine, a toxic alkaloid that inhibits cell mitosis; sometimes, even handling the flower alone can cause skin damage.

Chamaedrys (Teucrium chamaedrys L.), traditionally used for its bitter properties in digestive disorders but no longer used as it has been declared hepatotoxic by the Ministry of Health.

White Hellebore (Veratrum album L.), once used for treating hypertension, is no longer used due to the high toxicity of its alkaloids, among the most active in the plant world.

Ingestion causes burning sensation in the mouth, excessive salivation, tremors, vomiting, dizziness, and visual disturbances.

Great care must be taken in identifying this plant, especially for inexperienced gatherers.

Veratrum, in fact, has a morphology very similar to that of Gentian (Gentiana lutea L.), harvested for the preparation of liqueurs and digestives.

Another plant known for its hallucinogenic effect is Jimsonweed (Datura stramonium L.), whose leaves were used in folk medicine as a narcotic and muscle relaxant.

Ingestion of this plant leads to visual, auditory, tactile hallucinations, delirium, as well as dry mouth and mucous membranes, intense thirst, tachycardia, and muscle weakness.

Jimsonweed toxicity is due to the presence of tropane alkaloids (hyoscyamine and scopolamine).

It should be noted that all these plants, along with many others recognized as toxic, are not and cannot be used for health and medical purposes.

However, even when using species indicated for therapeutic purposes, caution must be exercised: the active principles contained within plants have a specific effect on our bodies depending on the dose taken; therefore, a substance cannot be defined as beneficial or toxic absolutely, and a plant can be both a remedy and a poison simultaneously.

In the 1500s, Paracelsus, a physician and alchemist, wrote:

“Nothing is poison, nothing is poison, it is the dose that makes the poison.”

It is therefore necessary to be aware of the dangers, sometimes very serious, that can be encountered in our health by using medicinal plants with uncontrolled dosages or concurrently with other synthetic treatments that may create interactions.

We emphasize how dangerous so-called “DIY remedies” can be, and for this reason, it is always necessary to have a specialized person who can define the dosages and methods of drug administration.

This is the case of Ginseng abuse syndrome, which occurs following high dosage of the drug and its prolonged use.

This adverse reaction is characterized by anxiety, insomnia, diarrhea, rashes, nervousness, euphoria followed by depression and high blood pressure.

Another plant whose use can only occur following a medical prescription is Foxglove (Digitalis purpurea L. – Digitalis lanata Ehrh.).

Digitalis leaves contain cardiac glycosides, indicated in therapy to improve myocardial function.

Medical supervision is essential in the use of this drug because the therapeutic dose is very close to the toxic dose.

There are also plants that are toxic only under particular conditions or when taken in a particular form.

This is the case of Castor Bean (Ricinus communis), whose seeds, if ingested, can be deadly.

Another example is common Sage, whose leaves have always been used as flavoring in cooking but also therapeutically for digestive disorders and excessive sweating; however, extreme caution is needed in the use of the essential oil: the presence of thujone and camphor makes it neurotoxic.

Both of these components have convulsant action, so Sage essential oil should only be taken under strict medical supervision and not in prolonged treatments.

Similarly, Hyssop essential oil (Hyssopus officinalis L.) is also reported to be neurotoxic and convulsant, so it should not be used.

There are also numerous plants, not used as medicines precisely because of their toxicity, that are very common in our gardens and therefore great care must be taken in case of accidental ingestion, especially if they are within reach of children.

Yew (Taxus baccata L.), a beautiful evergreen tree of considerable size, is toxic in all its parts.

Reported poisoning cases have occurred following ingestion of the “red berries,” which surround the seed containing toxic principles.

Another example is Oleander (Nerium oleander), a plant typical of maritime environments, which when ingested causes nausea and vomiting.

Even the common garden hedge of Cherry Laurel (Prunus laurocerasus) has leaves and seeds that contain toxic substances, as well as Peony (Paeonia officinalis), which is poisonous in all its parts and if ingested causes severe vomiting.

Of course, even plants that have been shown to be safe for use can cause adverse and unpredictable reactions.

We are talking about allergic reactions, which are immune and subjective reactions, quite different from cases of poisoning.