My first major point is that every illness, without exception, is an attempt by the body to eliminate mucus and, in advanced stages, pus (disintegrated blood). Every healthy organism of course must contain a certain amount of naturally occurring mucus, called lymph, the fatty mucus-like substance of the colon. Every medical expert dealing with cathartic problems, from a harmless runny nose to pneumonia and tuberculosis, will attest to this fact. But we are examining here a very unnatural and unhealthy mucus condition which is epidemic in modern society. The body's attempt to eliminate excess mucus is not always obvious in diseases of ears, eyes, skin diseases, stomach problems, heart trouble, rheumatism, arthritis, etc., not to mention in mental disturbances. And yet excess mucus is the main cause of the problem. Mucus, which can no longer be eliminated through natural means, enters the blood and reappears at a location where the blood circulation is reduced (perhaps because of a strong chill) as a heat symptom, an inflammation, a pain, or maybe a fever produced by the body.

If you put a sick person on a mucusless diet, say fruit, or even just water or lemonade, the energy usually used for digestion (and now free for the first time in decades) will immediately attack and try to dissolve the hardened masses of mucus that have accumulated in the body since childhood. And what is the result? With absolute certainty this mucus will manifest itself in the urine and feces. I call these hardened masses of mucus, present at the center of every pathological abnormality, the common root cause of every illness. If the disease is in an advanced stage, to the degree that there are pathological tissue changes deep inside ht body, you will also see the elimination of pus. As soon as the mucus-forming artificial food, like fat meat, bread, potatoes, pasta, rice, milk, etc. are discontinued, the bloodstream will attack mucus and pus and will eliminate both through the urine. In people with a high degree of mucus the body will use each and every body opening and elimination channel to rid itself of the poisons.

If you cook potatoes, flour, rice or meat long enough you will end up with gelatin-like, thick mucus substance. It looks very much like the glue that bookbinders and woodworkers use as adhesives. This mucus-like substance soon turns acidic, starts to ferment, and becomes the breeding ground for fungi, mold, and bacteria. In the digestive process, which is, chemically speaking, nothing but a kind of cooking and brewing process, this mucus-this glue-is separated out, because blood can only absorb the glucose which has been extracted from the carbohydrates. The remaining byproduct, the mucus or glue, is an alien substance for the body which must be eliminated completely from the earliest stage of life on.

Now it becomes clear that, in the course of a lifetime, the digestive tract and the colon are increasingly clogged up with mucus. This glue-like substance, the residue of plant and animal material, continues to ferment, and finally clogs up the arteries and affects the blood's ability to regenerate the whole system.

Source: The Cause and Cure of Human Illness (p.2)
Kranke Menschen by Professor Arnold Ehret