'Fighting Poison with Poison' Is Not as Simple as It Sounds

Almost everyone who has studied TCM knows of a treatment called "fighting poison with poison." As a four-character idiom, the phrase is known to every man, woman, and child in the Chinese-speaking world. But the great majority of people understand only its surface meaning, unable to see that behind "fighting poison with poison" lies a very complex scientific principle.

Toxins are substances widespread in nature, and humans have also learned to synthesize many kinds. Not only are some organisms poisonous; many lifeless substances are poisonous too. Since humanity began, we have been in constant contact with poisons.

Poisons even drove our own evolution in nature. Lynne Isbell, an anthropology professor at the University of California, Davis, proposed a theory called the Snake Detection Theory. She argues that deadly venomous snakes had a profound influence on us humans, and that the evolution of the human brain was likely driven by snakes.

Roughly sixty million years ago, snake venom became more potent in Asia and Africa, and snakes had been preying on mammals for millions of years. To escape snake predation, mammals had to evolve better vision; better vision required a correspondingly developed visual nervous system, which drove the evolution of the human brain. The human brain grew larger and larger in this process, and as cranial capacity increased, human intelligence grew day by day.

Poisons have also helped the earth maintain ecological balance and helped humanity control excessive population growth, in which mosquitoes have made the greatest contribution. This is not to say that mosquito venom itself is terrible, but rather that mosquitoes serve as intermediate hosts transmitting many diseases that cause huge numbers of deaths and injuries every year. Malaria, transmitted by mosquitoes, takes more than 600,000 lives a year; yellow fever can kill 30,000; dengue fever causes 12,000 deaths; epidemic encephalitis claims more than 20,000; and chikungunya, West Nile fever, Rift Valley fever, Zika virus, and other encephalitides can also be spread by mosquitoes. As many as 40 million people suffer from lymphatic filariasis (elephantiasis) transmitted by mosquitoes.

Why are mosquitoes such efficient virus transmitters? This is thanks to mosquito venom. Mosquitoes inject venom into the human body to achieve blood-sucking; they use the vasodilators, anticoagulants, and anti-platelet agents in mosquito venom to keep the wound open while they feed. The anti-inflammatory compounds in mosquito venom prevent the immune system from signaling that the body has been attacked; most of the time, by the time we realize we have been bitten, the mosquito has long flown away. The wound the mosquito makes in our body creates the conditions for the various germs harbored inside it to invade. The tiny mosquito is simply a master natural compound factory.

From the human standpoint, mosquitoes are a hateful pest, but from the standpoint of maintaining ecological balance in nature, mosquitoes are meritorious. Without the various diseases mosquitoes transmit, the earth's human population would be terrifyingly large, and the pressure that excessive population puts on the ecological environment might long have destroyed our own species.

So we humans are, from birth, a species that coexists with poisons on earth, and poisons have also advanced human medicine. On the one hand, people who are poisoned need emergency rescue; on the other hand, various toxins are also excellent medicines that can cure many diseases. Human medicine has continually advanced through treating poisoning and using toxins to heal.

For example, botulinum toxin is the most lethal toxin known on earth to humans—a mere 60 nanograms (one nanogram is one-millionth of a milligram) is enough to kill a person, and to kill every human on earth, one need only grab a handful of botulinum toxin. But injecting a trace amount of botulinum toxin into the forehead can effectively smooth out forehead wrinkles. Some of the drugs humans commonly use to treat hypertension are also refined from a snake venom.

Chinese medicine contains a large number of "fighting poison with poison" drugs—arsenic (pi-shuang), cantharis, toad, nux vomica, gamboge, and the red beetle are all highly toxic medicinals with very low lethal doses. But the reason they can treat disease is precisely their toxicity. Arsenic trioxide, the main component of arsenic, though highly toxic, kills many kinds of cancer cells, with an effective rate as high as 85% in patients with acute promyelocytic leukemia (APL).

Human immunity has also been continuously strengthened through contact with poisons. Poisons train our immune system, making us less fragile. For thousands of years, it has been with the help of viruses, bacteria, and toxins that we evolved in nature into what we are today.

The mammalian immune system has two parts: the innate immune system and the adaptive (specific) immune system. The innate immune system is our first line of defense against viruses, bacteria, and toxins. Our bodies have many ways to prevent foreign particles from harming our vital tissues and organs; the mucous layers of our skin, nose, throat, and intestines are both natural physical barriers and secrete antimicrobial compounds. Once a harmful substance invades, they rise up to fight and protect our bodies.

If this barrier is breached, our innate immune system immediately kicks in; injured or infected cells release compounds that tell nearby immune cells to destroy the invaders. In the course of fighting harmful viruses, bacteria, and toxins, our bodies also produce antibodies that resist a specific germ or toxin; the next time that germ or toxin attacks, the antibodies in our body help us resist it—this is how vaccines and antivenoms in modern medicine are produced.

However, the development procedures for many antivenoms used in humans are very complex and require the help of large mammals such as horses and sheep. To make snake antivenom, for instance, one first injects snake venom into a horse's body so that its blood system produces antibodies against the venom and resists the damage it would otherwise cause. Then, through very complex purification, the snake-venom antiserum is refined from the horse's blood to treat humans bitten by snakes. For some novel viruses, we can also use this principle to produce serum to treat critically ill patients; this is called serum therapy.

Our body's ability to develop immunity against poisons also creates quite a few problems when using poisons to treat disease. In a chronic disease like cancer, which requires long-term treatment, doctors can only use small doses of toxic drugs to kill the body's cancer cells. After these toxic drugs are used for a long time, the patient's body develops corresponding specific immune function that resists the drugs' action; this is one reason many cancer patients develop drug resistance. Whether in Chinese or Western medicine, the principles of curing disease have much in common, and the principles of drug resistance have much in common too. That is why, when I personally use the "fighting poison with poison" method to treat cancer, I frequently change the drug combinations to address resistance.

Toxic drugs treating disease also have many side effects. Anti-cancer drugs, for instance, kill not only cancer cells but also normal cells, and they produce toxic side effects on vital organs such as the liver and kidneys. Some toxic drugs damage the digestive system; some damage the nervous system; others damage the heart and blood vessels. Today, when we use the method of fighting poison with poison, we can no longer remain at the rough ancient level; we must draw on modern scientific research into toxicology and pharmacology and do more refined work to improve the efficacy and safety of treatment.