The Kidney governs the lower part of the body and serves as the root of the entire organism. The feet are the external manifestation of Kidney function. If individuals damage their bodies through excessive indulgence in desires, they often remain unaware, leading to internal deficiency of Kidney Qi (Kidney Energy) and failure of the True Yuan (Primal Essence) to be retained. Under such conditions, if one suddenly stands on cold ground, sits for long periods in low-lying damp places, bathes with cold water immediately after exposure to intense heat, or walks on frost in the early morning, one may contract Hong Kong Jiao (Foot Qi Disease, also known as Beriberi) from inadvertently contracting the four pathogenic factors (Wind, Cold, Summerheat, Dampness).

Although Hong Kong Jiao originates in the feet, it actually circulates throughout the body. Symptoms may include high fever and headache, cold pain in the body, spasms and cramping of all joints, wandering pain in the ten fingers, sudden convulsive pain, numbness in the lower abdomen, progressing to chest fullness and panting, irritability and palpitations, confusion and photophobia, forgetfulness and erroneous speech, abdominal pain with diarrhea, vomiting of phlegm-saliva, aversion to food odors, vomiting upon seeing food, and frequent constipation of both stool and urine. From the thighs to the knees, and from the calves to the ankles, there may be weakness in flexion and extension, stubborn paralysis, cramping, soreness, and pain; the skin color may remain unchanged, or there may be swelling or no swelling. These are all its clinical manifestations. If accompanied by spontaneous sweating and aversion to wind, anhidrosis and aversion to cold, or alternating chills and fever, the pathogen transmits into the Foot Six Meridians. The external signs resemble Shanghan (Cold Damage), except for the sudden onset of foot pain.

The treatment method requires investigating the origin of the pathology: cases complicated by Wind feature wandering pain with sweating; those complicated by Cold feature pulling pain and cramping; those complicated by Summerheat feature extreme thirst and heat-induced irritability; those complicated by Dampness feature swelling, fullness, heaviness, and stagnation. When the four pathogenic factors coexist, one must deduce which factor is predominant and address it accordingly. Prescribing medicine against the specific disease requires careful weighing of factors. However, ancient physicians named this condition "Huan Feng" (Slow Wind), attributing it to Wind-Toxin. Therefore, the general treatment principle primarily involves unblocking the bowels to allow the expulsion of toxic gases before recovery can occur, but the dosage must not be excessive. Decoctions for tonification and washing therapies are strictly prohibited by medical experts.

Although the treatment of Hong Kong Jiao prioritizes the dispersion and drainage of toxic gases—because death is feared due to excess pathogenic qi—the meridians of the interior and exterior differ, and cold and hot syndromes present differently. Some cases arise subsequent to other diseases, while others lead to the succession of new diseases; thus, flexibility in treatment is essential. The principles state: warm what is cold, cool what is hot, disperse what is in the exterior, purge what is in the interior, support and nourish the center when the Great Void (Tai Xu) lacks Qi, and apply warming and draining methods for congealed Yin harboring toxins. These constitute flexible therapeutic strategies within the chest/mind. If treatment is delayed, allowing toxic gases to enter the abdomen and rush toward the Heart, causing attacking pain, wheezing, chest fullness, upward rushing of Qi, and abnormal vomiting, the condition gradually deepens into a critical stage, potentially leading to sudden death.