This section is from the "Nature Cure: Philosophy and Practice Based on the Unity of Disease and Cure" book, by Henry Lindlahr.
In the treatment of chronic diseases some advocates of natural methods of healing still favor warm or hot applications in the form of hot-water baths, different kinds of steam or sweat baths, electric light baths, hot compresses, fomentations, etc.
However, the great majority of Nature Cure practitioners in Germany have abandoned hot applications of any kind almost entirely because of their weakening and enervating aftereffects and because in many instances they have not only failed to produce the expected results, but aggravated the disease conditions.
We can explain the different effects of hot and cold water as well as of all other therapeutic agents upon the system by the Law of Action and Reaction. Applied to physics, this law reads: "Action and reaction are equal but opposite." I have adapted the Law of Action and Reaction to therapeutics in a somewhat circumscribed way as follows: "Every therapeutic agent affecting the human organism has a primary, temporary, and a secondary, permanent effect. The secondary, lasting effect is contrary to the primary, transient effect."
The first, temporary effect of warmth above the body temperature, whether it be applied in the form of hot air or water, steam or light, is to draw the blood into the surface. Immediately after such an application the skin will be red and hot.
The secondary and lasting effect, however (in accordance with the Law of Action and Reaction), is that the blood recedes into the interior of the body and leaves the skin in a bloodless and enervated condition subject to chills and predisposed to "catching cold."
On the other hand, the first, transient effect of cold-water applications upon the body as a whole or any particular part is to chill the surface and send the blood scurrying inward, leaving the skin in a chilled, bloodless condition. This lack of blood and sensation of cold are at once telegraphed over the afferent nerves to headquarters in the brain, and from there the command goes forth to the nerve centers regulating the circulation: "Send blood into the surface!"
As a result, the circulation is stirred up and accelerated throughout the system and the blood rushes with force into the depleted skin, flushing the surface of the body with warm, red blood and restoring to it the rosy color of health. This is the secondary effect. In other words, the well-applied cold-water treatment is followed by a good reaction and this is accompanied by many permanent beneficial results.
The drawing and eliminating primary effect of hot applications, of sweat baths, etc., is at best only temporary, lasting only a few minutes and is always followed by a weakening reaction, while the drawing and eliminating action of the cold-water applications, being the secondary, lasting effect, exerts an enduring, invigorating and tonic influence upon the skin which enables it to throw off morbid matter not merely for ten or fifteen minutes, as in the sweat bath under the infiuence of excessive heat, but continually, by day and night.