The Medicine Travels the Whole Body — So Why Does It Work Only Where It Hurts?

"How does a medicine I swallow find my aching knee?"

When I get this question in the clinic, I pause for a moment. It is a good question.

Medicine enters through the mouth, passes the stomach and the intestines, rides the blood, and travels evenly through the whole body. It does not go only to the knee. It goes to the fingertips, and to the roots of the hair.

And yet the effect appears at the knee.

The common answer is "the medicine finds the place that hurts." I do not use that explanation. The medicine does not know the way. It is not searching for anything.

My answer lies on the opposite side. What has gone somewhere is not the medicine — what has changed is the site.

What is different about a site that has broken down

When some site of the body has hurt for a long time, the conditions there come to differ from those of a healthy site.

It tilts toward acidity. Oxygen runs short and metabolic waste piles up. There are values measured in people: the joint fluid of a rheumatoid joint runs down to pH 6.0. Not a guess — a measured number.

The receiving side grows sensitive too. The number and the sensitivity of the receptors that take in signals shift, so the same signal meets a different response.

   Healthy tissue                  Broken-down tissue
 ─────────────────            ─────────────────
  Acid-base balance kept       Tilts toward acidity (to pH 6.0)
  Receptor response stable     Receptors sensitive / dulled
 ─────────────────            ─────────────────
        ↓                             ↓
   Medicine passes through     Medicine wakes up at that site

Acidity is the key

Let me go a little further here. It looks difficult, but the principle is simple.

A large share of herbal ingredients put on a coat as they are absorbed. In the liver and the gut something like a sugar attaches, so they dissolve well in water and travel well — but their action is folded away for the moment. Draw blood and measure, and it is mostly this coated form you catch.

There are scissors that take the coat off. They are an enzyme released by the immune cells at an inflamed site, and these scissors cut well when the surroundings are acidic.

So it goes like this.

1. A broken-down site is short on oxygen, waste piles up, and it turns more acidic than its surroundings
2. At that acidic site, the scissors cut well
3. The coat comes off, and the acting form is released right there
4. A healthy site is not acidic, so the ingredient passes through still wearing its coat

The medicine did nothing at all — the environment of that site woke it up.

There is research in animals that checked this directly. When the clothed form was put into the bloodstream, the active form ran 2.5 times higher in the inflamed ear than in the healthy ear on the other side. The amount of the clothed form itself was similar on both sides. The compound did not travel to that place — it was undressed there.

And so the low concentration of herbal medicine is explained

In another article I have written about the paradox of concentration in herbal medicine. The story was that the concentration at which herbal ingredients remain in the blood is, by the standards of modern drugs, surprisingly low — and yet the body clearly responds. (Why Herbal Medicine Works — The Paradox of Concentration)

Adding the view of this article loosens that paradox a little.

The concentration measured in blood and the amount actually working at the broken-down site are two different stories. What you measure from drawn blood is an average across the whole body, and mostly the coated form at that. Even when the average is low, at a site whose environment has changed, the ingredient wakes up.

Working where it is needed without pushing evenly on the whole body — I see this as one reason herbal medicine has carried relatively little burden even over long use.

Still, acid and base are not all of it

To stop here would be to tell half of it. I am wary of the temptation to translate every disease into the language of acid and base.

The conditions of the body are set by several axes together. There is physical stiffness and pressure, there is chemistry, and metabolism and immunity and the nervous system and circulation stand alongside them. There is no higher or lower among these axes. The axis that tilts first differs from disease to disease, and when one tilts, the rest are shaken in a chain. (What Herbal Medicine Actually Does)

In a person whose long-standing diarrhea has drained their energy and left their hands and feet cold, the language of pressure hardly appears at all. The immunity of the gut mucosa was shaken first, absorption broke down, energy metabolism sank with it, and peripheral blood flow fell away. What this person needs is not to have pressure lowered but to have the gut settled and absorption revived.

Conversely, in a person whose lower abdomen has grown taut and is pressing on a nerve, the physical axis is the protagonist.

Reading which axis tilted first — I think that is what clinical practice is. And so the goal of treatment, too, is not to swap out a part, but to bring the environment back so the body can settle itself.

That tissue with long-standing inflammation tilts toward acidity is a fact measured in people, and that ingredients put on and take off a coat, and that those scissors cut well in acidity, have been confirmed as well. Most of that, though, comes from cells and animals. How large this runs in the human body, at the low concentrations of herbal medicine, has not yet been confirmed enough. There are many diseases this frame does not explain, and when herbal medicine cannot help a disease, I say that it cannot.

How these conditions are read in practice — what the hand feels for, and how the old texts' "blocked places" and "pooled places" carry over into today's words — I have written about elsewhere. (How does the medicine find the painful place)

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When a patient asks me, "Why does this medicine work for me?", instead of naming an ingredient, I say this.

The medicine did not find your knee. Your knee had changed, and so the medicine woke up there.

So even after treatment ends, the work of protecting that site's environment remains. If there is a disease that returns when you stop the medicine, it is not that the medicine was insufficient — it is that the environment was still the same.

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References

• An ingredient circulating in its coated form, once an enzyme took the coat off, became the active form and moved immune cells — Immunity, Inflammation and Disease, 2017
• How an ingredient's coat comes off inside inflamed immune cells and is released as the active form — PLoS One, 2013
• Where the acid-base state of tissue meets inflammation — a review of values measured in human inflamed tissue — Trends in Immunology, 2023

Written by Dr. Heo Ji-young (PhD in Korean Medicine Pathology, Kyung Hee University · former Research Professor of Herbology, Kyung Hee University)