From the point of view of Chinese pathology, eczema is also due to an inborn deficiency of the Lung and Kidney’s Defensive-Qi systems. The relationship between the Lungs and skin is well known and yet, when discussing the pathology of skin diseases, Chinese books always seem to stress more the role of Blood (and Liver) in connection with the skin.
In the case of atopic eczema and asthma, the connection between the Lungs and the skin could not be clearer. These two symptoms are very clearly related, and often one will appear as the other improves. For example, often eczema appears first at a very early age or even from birth, to be followed later by asthma when the child is about 4 or 5 years old. This pattern is more likely to occur if the eczema is suppressed with the application of cortisone creams. The reverse may also occur when asthma appears first and then apparently improves only to be followed by eczema.
The relationship between skin diseases and the Lungs can also be observed in the action of many of the herbs that are used to expel Wind in skin diseases. The same herbs that expel Wind from the skin in eczema or rashes also stimulate the diffusing and descending of Lung-Qi in exterior conditions.
The Kidneys also play a role in the pathogenesis of eczema. First of all, while the Lungs control the skin in the sense of being linked to its pores, the Kidneys nourish and moisten the skin. Second, as mentioned before, the Kidney-Essence is closely bound with the Corporeal Soul (Po) of the Lungs, which manifests on the skin and which is responsible for sensations of itching and pain on the skin. An inborn defect of the Kidney-Essence, such as occurs in atopic asthma and eczema, can therefore affect the Corporeal Soul and the skin. Third, the Extraordinary Vessels, especially the Penetrating (Chong) and Directing (Ren) Vessels, nourish the skin through a network of secondary vessels all over the body. Because these two vessels arise from the Kidneys and spread the Kidney-Essence to the skin, they provide a further link between the Kidneys and the skin.
Eczema from Wind-Heat is characterized by skin lesions that are very dry, red and itchy, with the itchiness being spread all over the body and moving from place to place. Eczema from Damp Heat is characterized by skin lesions that are moist, oozing fluid, red and itchy, with the itchiness being more confined to specific parts of the body, often the forearm and lower leg.