The skin is the body’s largest organ. It consists of a thin outer layer called the epidermis and a much thicker inner layer called the dermis. Beneath the dermis is a layer of little lobes of fat bound together by tough fibers that extend down from the dermis. Between the epidermis and dermis is the basement membrane, to which both layers are attached. This characteristic layering of cells, from the live and actively replicating cells of the stratum germinatum to the dead flakes on the surface, provides the unique setting for the skin diseases.
The skin fulfills a number of important functions. As the interface between the body’s internal structures and the environment, the skin serves as a protective coat for the body against mechanical injury and attack by bacteria, fungi, viruses, and parasites. The pigment melanin protects against ultraviolet radiation. The skin is also a major organ of elimination through the functions of sweating and sloughing off dead skin cells. In addition, a number of immune responses occur in the skin.
In various ways, the skin also plays a vital role in temperature regulation. Variable amounts of heat are lost through the skin by transfer from the dermis capillaries to the cooler epidermal cells. The amounts lost vary according to constriction or dilation of the dermal blood cells. The layer of insulating fat modifies the amount of heat conducted from the depths of the body. Sweating cools the epidermis through evaporation.
The skin also serves as a primary sensory organ. The five sensations that arise from stimulation of skin nerves are touch, pain, heat, cold, and pressure. Other skin sensations, such as vibration, are composites of these basic sensations. In hairy skin, the nerve endings are simple, threadlike, naked terminals. In skin that is not hairy, there are several types of specialized nerve endings. Although they look the same, each nerve ending is capable of responding to only one of the five basic types of sensation.
Finally, the skin is the interface between our consciousness and the world, the vehicle through which we express, communicate, and perceive. Thus, psychological and spiritual aspects of the individual impact and are impacted by the skin.
This array of functions highlights the complexity of the relationships among the skin, the internal organs, and the psychology of the individual. From this awareness comes an important therapeutic insight: Effective phytotherapeutic treatment of skin disease must be mediated through internal medication, not topical application.
Treatment of skin problems must take into account the whole panoply of issues involved. Similarly, the widely held view that many skin problems are caused by “nerves” is not very helpful. There is a deep and complex relationship between the epidermis and the nervous system. Developmentally, nerve and skin cells derive from the same tissue in the human embryo. The close functional relationship between the skin and the nervous system facilitates many aspects of homeostasis, such as body temperature control.
In addition, the psychological relationship between the individual and the skin is deep and complex. An individual expresses and experiences much of his or her self-image through the skin. Thus, perception of the world and communication to the world are also vital skin functions.
To conclude that there is a simple causal relationship between the nervous system and skin disorders ignores all of the insights gained through the holistic perspective. Anyone with obvious skin problems may well become stressed, developing psychological coping mechanisms that appear to be manifestations of nervous system issues. But which comes first?