The pathological characteristics of the infants include two aspects: easy contraction and rapid transmission, pure zang-qi and easy rehabilitation. 

Susceptibility to diseases means that the infants are subject to the invasion of pathogenic factors. The infantile viscera are delicate and the resistance of the body is weak. Furthermore, the infants are unable to take care of themselves in terms of food and daily life. So they are liable to the attack by six exogenous pathogenic factors and impairment by improper diet. With the other congenital pathological factors, the infants are susceptible to the attack by exogenous pathogenic factors. The younger the infants are, the higher the morbidity will be. 

The lung is a delicate organ governing respiration and being related to the skin and hair. Since the infants are usually deficient in the lung and the function of defending the superficies is weak, pathogenic factors can invade the lung either from the nose and mouth or from the skin and hair. Therefore, it is said that the pathogenic cold attacks the lung and the upper invasion of warm pathogenic factors affects the lung first. During the infancy, the infants are liable to disorders of the pulmonary system, such as common cold, cough, pneumonia and dyspnea with cough.

Since the infants are insufficient in the spleen and weak in transformation and transportation, they are likely to be affected by improper feeding, leading to such symptoms as anorexia, retention of food and diarrhea. Since the spleen is often insufficient, the food and water taken into the body cannot be transformed into cereal nutrients, leading to insufficiency of the production of qi and blood, which further results in asthenia of qi and blood and poor development.

Constant asthenia of the infants refers to insufficiency of infantile kidney essence. Essence includes prenatal essence and postnatal essence. The former is stored in the kidney and the latter is derived from the spleen. Before the infant birth, the prenatal essence nourishes the postnatal essence. That is to say, the prenatal essence promotes the development of the postnatal essence. After the infant birth, the postnatal essence nourishes the prenatal essence. That is to say, the cereal nutrients transformed by the spleen and stomach infuse into the kidney when it is abundant. 

The pathological implication of constant asthenia of the kidney refers to various diseases likely to be caused by insufficiency of the congenital kidney essence, such as metopism, timidity, weakness, five kinds of retardation and five kinds of flaccidity. It may also refer to such pathological conditions as rickets caused by insufficiency of gastrosplenic essence which affects the function of the kidney to store essence.

The infantile abundance of the liver physiologically signifies the vigorous development of shaoyang like sprouting of plants. However, this expression also implies pathological changes, such as sthenic syndromes due to flaring up of liver fire and hyperactivity of liver yang as well as appearance of wind syndrome, convulsion and coma due to high fever.

Fast transmission means that in the course of development, the infantile diseases are liable to changes marked by susceptibility to asthenia and sthenia, and susceptibility to cold and heat.

Asthenia and sthenia refer to the conditions of the healthy qi and the pathogenic factors. Susceptibility to asthenia and sthenia means when the infants are ill, the pathogenic factors tend to be sthenic and the healthy qi tends to be asthenic, and that the sthenic syndrome can immediately transform into an asthenic one and vice versa or simultaneous appearance of both the asthenic and sthenic syndromes. 

Take pneumonia for example. At the early stage, stagnation of the lung qi may bring on fever, cough, sputum rale and dyspnea. Missed or wrong treatment will lead to pale complexion, cold limbs, profuse sweating, cyanosis of the lips and palpitation which manifest as the asthenic syndromes due to penetration of the pathogenic factors with asthenia of the healthy qi and sudden loss of the heart yang. Take infantile diarrhea for another example. 

At the primary stage, improper diet or stagnation of the pathogenic factors may bring on such sthenic syndromes as abdominal distension, diarrhea with acid and putrid odour, scanty brownish urine, reddish tongue with greasy fur, slippery and forceful pulse. If diarrhea is not stopped, it will lead to consumption of body fluid or exhaustion of yin and loss of yang, immediately resulting in dry lips, no tears, unconsciousness, cold limbs, thin and weak pulse. Such a quick change of pathological conditions is typical among the infants.

Cold and heat are the generalization of the nature of the pathological changes, while the symptoms of cold and heat mean the clinical manifestation of symptoms due to the difference of the pathological nature, or the transformation of the pathological nature under certain circumstances during the development of the disease. Susceptibility to cold and heat means that the infants present with heat syndrome in the course of a disease because of their immature yin. 

So the syndrome is liable to be characterized by impairment of yin due to excess of yang appearing in heat syndrome. On the other hand, the delicate body of an infant due to immature yang is liable to cause yang deficiency or yang exhaustion and yin-cold syndrome occurs. Take the cold syndrome caused by attack of cold and wind for example. The pathogenic factors can be stagnated to transform into heat, the extreme development of which generates wind, leading to heat syndrome marked by high fever and convulsion due to interaction of wind and fire. 

As to the infants with convulsion, apart from high fever, convulsion and internal closure due to interaction between wind and fire, they may manifest asthenic cold syndromes marked by such symptoms as pale complexion, sweating, cold limbs, weak and indistinct pulse. These are the manifestations of infantile susceptibility to cold and heat. 

In short, the changes of cold and heat as well as  asthenic and sthenic syndromes in the infants are quicker and more complicated than those in the adults. Therefore in the treatment of infantile diseases, correct differentiation of syndrome, accurate diagnosis and timely treatment are very important.

Although the pathological transmission in the infants is fast and the transformation from cold to heat and from asthenia to sthenia in the infants are complicated, the regeneration and repair of the tissues are strong due to the purity of the infantile body, vigorous development and full vitality. Furthermore, the causes of infantile diseases are usually simple. During the course of the pathological development, fewer mental factors are involved. That is why infantile diseases are easier to cure. 

Even serious diseases can be cured if timely treatment is given and proper cares are taken. Take diseases of the lung system, spleen system and pestilence for example. Though they are commonly encountered, most of them have shorter duration and are quicker to heal. Even some diseases with longer duration, such as infantile malnutrition, can also be cured quickly through replenishing qi and blood, regulating diet and adapting to the climate.