Low-grade fever in children refers to a fluctuation in body temperature between 37.5 and 38 degrees Celsius. It is often accompanied by symptoms such as anorexia, lack of strength, and mental fatigue.

This condition is referred to as "warmth and robustness" in Zhubing Yuanhou Lun, and Zhengzhi Zhunsheng explains it as: "A mild warmth that is not very intense is called warmth and robustness." Ancient medical texts rarely discussed low-grade fever in children as a separate topic, but in recent years, it has not been uncommon. To facilitate clinical differentiation, a dedicated discussion is provided here.

bubble_chart Pattern Analysis

1. Pathogenic Factors Lingering in the Lung-Defensive︰Persistent low-grade fever, mild in intensity with slight aversion to wind and cold, nasal congestion, runny nose, dry cough with scant sputum, red tongue with thin white coating, rapid or floating pulse, and floating red finger venules. This condition is often caused by unresolved external contraction of wind pathogens, leading to lingering pathogens in the lung-defense system that stagnate and generate heat. It is commonly seen in winter and spring, characterized by mild fever, slight aversion to wind and cold, accompanied by nasal congestion, runny nose, dry cough with scant sputum, and floating red finger venules. Treatment should focus on dispersing wind and releasing the exterior, and Lonicera and Forsythia Powder may be selected.
2. Dampness-heat︰Persistent low-grade fever, though temporarily relieved by sweating but recurring afterward, especially pronounced in the afternoon, accompanied by anorexia, nausea, loose stool, scanty urine, thirst without desire to drink, a red tongue with greasy coating, and a soggy rapid pulse, with faintly concealed finger venules. It is often caused by exposure to summerheat-dampness pathogens, which accumulate in the triple energizer and steam to generate heat. It commonly occurs during summer and autumn. The key diagnostic points are: prolonged duration, temporary relief through sweating but recurrent fever, accompanied by anorexia, nausea, loose stool, scanty urine, and concealed finger venules. Treatment should focus on clearing heat and resolving dampness, using the formula Sweet Dew Detoxicating Pill with modifications.
3. Food Retention in the Spleen and Stomach︰Hiding fever, more pronounced in the afternoon, abdominal distension and fullness, belching with foul odor, loss of appetite, nausea and vomiting, loose stools that are foul-smelling or constipation, thick and greasy tongue coating, slippery and solid pulse, and purple and stagnant finger veins. It is a condition of excess complicated by deficiency, often caused by improper diet, excessive consumption of raw, cold, or greasy foods, leading to dysfunction of the spleen and stomach in ascending and descending, impaired transportation and transformation, and stagnation of undigested food, which then generates heat. Hiding fever, more severe in the afternoon, accompanied by symptoms of food stagnation such as abdominal distension and fullness, belching with foul odor, foul-smelling stools, and greasy tongue coating. Treatment should focus on promoting digestion and removing food stagnation, invigorating the spleen and harmonizing the stomach. The recommended formula is Harmony-Preserving Pill with modifications.
4. Malnutrition and Food Retention︰Persistent low-grade fever, weak constitution, withered hair, dull eyes, drowsiness and reluctance to speak, craving for food or hunger with vomiting and nausea, constipation or loose stools, abdominal distension and fullness with palpable lumps, pale red tongue with thin white coating, thready and weak pulse, floating and faint sluggish fingerprints. This indicates deficiency with excess. It is caused by improper feeding, premature weaning, partiality for certain foods or peculiar tastes, excessive consumption of rich and sweet foods, or congenital spleen-stomach weakness leading to impaired transportation and accumulation of milk and food, eventually developing into malnutrition and consuming qi and yin, resulting in fever. Clinical differentiation shows persistent low-grade fever accompanied by withered hair, emaciation, listlessness, and abdominal lumps, which are symptoms of infantile malnutrition with accumulation. Treatment should focus on eliminating malnutrition and strengthening the spleen, nourishing the stomach and harmonizing the middle, using Xiaogan Li Pi Tang with modifications.
5. Qi Deficiency︰Low-grade fever, profuse sweating, worsened by activity, fatigue, lack of strength, shortage of qi, reluctance to speak, shortness of breath upon exertion, complexion shallow yellow, poor appetite, swollen and tender tongue with tooth marks on the edges, scant tongue coating, weak or floating and large pulse, pale red and floating finger venules. Mostly due to constitutional weakness, postnatal malnutrition, original qi not being robust, or after other illnesses, damage to middle qi, with yin fire floating upward causing fever; yin-deficiency fever, mostly due to Rebing damage to yin, consuming body fluids, leading to yin failing to restrain yang and thus fever. Or constitutional yin deficiency, often triggered by external factors causing internal heat. The fever from qi deficiency manifests as fatigue, reluctance to speak, generalized fever upon exertion, along with pulse and symptoms of qi deficiency; the fever from yin deficiency is more pronounced in the afternoon, with flushed cheeks, night sweats, dry mouth and throat, and a thin, rapid pulse. The former should be treated by tonifying qi and strengthening the spleen, relieving fever with sweet and warm herbs, commonly using Middle-Tonifying Qi-Replenishing Decoction.
6. Yin Deficiency︰Afternoon fever, or steaming bone fever gradually intensifies, flushed cheeks, night sweats, dry mouth and throat, thirst with little desire to drink, dry stools, mild cases may only feel facial heat, red tongue texture, scant or no coating, thin and rapid pulse. Treatment should focus on nourishing yin and clearing heat. Commonly used formulas include Gentian Turtle Carapace Decoction or Bone-Clearing Powder, among others.

bubble_chart Documentation

1. Xiao'er Yaozheng Zhijue．Volume 1: "Warm strength is warm but not hot."
2. 《Pediatrics Zhengzhi Zhunsheng．fever》: "Warm strength is similar to high fever but with slight differences. Continuous heat is high fever, while a mild warmth that is not very intense is warm strength."
3. 《Pu Fu-zhou's Medical Experience》: "External-contraction fever, if treated improperly or not managed well, or if the constitution is inherently weak, often leads to low-grade fever. Long-term internal damage low-grade fever can be divided into qi deficiency and blood deficiency, with more cases belonging to the qi aspect and fewer to the blood aspect."