Photograph by Jan Vermeer / Minden Pictures
“All substances are poisons; there is none which is not; the dose differentiates a poison from a remedy.”
A toxin is a substance produced by a living organism that can cause harm, disease, or death when present in the body. Organisms that inject their toxins (through wounds, stings, and bites) are considered venomous, while those whose toxins are ingested are called poisonous. Toxicity can be found across many kingdoms on the tree of life—including animals, plants, and fungi—and it fruits with wisdom. As Swiss physician and alchemist Paracelsus, often recognized as the father of both modern medicinal chemistry and toxicology, famously noted: the dose makes the poison.
The plant kingdom produces some of the deadliest poisons known to humans. The most toxic plant in North America, water hemlock, is often fatally confused with parsnip and celery. Deadly nightshade (also known as belladonna) produces sweet berries that, when ingested, can paralyze muscles—including the heart. The oleander, with its beautiful pink petals, is so poisonous that even eating honey produced by bees that pollinated it can make you ill. The most deadly plant, though, is arguably tobacco; not only is it toxic to ingest, smoking it results in more than 5 million deaths every year. Sometimes, the most potent poisons are hidden in plain sight.
Fungi can be far more deceptive in their toxicity. Destroying angels are highly poisonous, yet often mistaken for edible meadow and button mushrooms. Death caps resemble harmless straw and caesar’s mushrooms, but produce a poison that can withstand even the hottest cooking temperatures and then induce violent side effects that turn lethal in half of cases. Deadly and fool’s webcaps produce side effects similar to the common flu, but left untreated, can lead to organ failure weeks later. Fly agarics, with their spotted red caps, might be recognized from fairy tales and children’s books—but when eaten, can result in delirium, seizures, and even comas.
But toxicology isn’t always black and white. Some of the world’s most venomous animals also carry the capacity for healing. Snake venom has been used to create a variety of life-saving medicines. Stonefish spear unsuspecting victims with lethal toxins, but they are also considered a delicacy in some parts of the world. Gila monsters have the most painful bite of any vertebrate due to their potent venom, though a hormone it contains is used to treat diabetes. Similarly, funnel web spiders are the most toxic arachnids—to humans and primates anyway, not other animals—but their venom could also treat heart attacks. Poison often comes down to context.
In fact, just about anything in excess can be poison. Despite how culturally ubiquitous it is, alcohol becomes toxic when we drink enough of it. Even substances we need in order to survive can kill us in excess; we will die without water, and yet too much of it can lead to water poisoning, causing our fluid-regulating sodium levels to plummet and our cells to swell. Then again, too much sodium in one’s diet can be lethal too, along with iron. And then there are the many medicines we rely on, which can save lives in the right doses and end them in others.
In abstract terms, the same can also be true. We live in a culture of extremes, when what we often need is moderation. Too little self-reflection can stunt personal growth, but too much of it can make us self-absorbed. Too little compassion can make us unkind, while too much of it can lead us to be taken advantage of. Too little vulnerability can close us off, whereas too much can expose us to harm. Too little ambition can render us lethargic, and too much can foster greed. Too little entertainment can make life feel joyless, yet too much can manifest as escapism.
While no doubt beautiful and tempting, the trappings of a society built on immoderation are deceitfully toxic—both for us and our planet, which is being poisoned by excess greenhouse gasses, waste and chemical pollution. But there is a remedy, one that we can practice embodying in our everyday lives. From the compositions of organisms to the equilibrium of ecosystems, everywhere we look in nature, we see the necessity of balance. That’s what our world needs now more than ever. Because if excess is poison, balance is the medicine.