皮肤由表皮，真皮和皮下组织这三层构成。表皮是通常不含有血管或神经的外侧皮肤。表皮外层脱落的死细胞称之为角质层cornified layer或颗粒层stratum corneum。表皮通常是坚韧的，因为它含有角蛋白，角状物质。角质层下面的浅层就是所谓的透明层。
皮肤的第三层，叫做皮下组织，位于真皮的下方。该层是由具有隔离能力的脂肪组成(Clark & Cumley, 1973)。
SKIN AND PSYCHOSOMATICS皮肤与心身医学（待译）
The skin, being the protective surface of the body, is exposed to numerousharmful influences, and the nerve endings in the skin are recipients of a great vaiiety of antigens. The skin is highly sensitive to pain,which can be elicited by physical and psychological factors. Most skin diseases are not lethal, but they are usually quite painful and may seriously affect the physical and mental functioning of an individual (Medansky,1980).
Psychological factors and especially emotions exert considerable influences on the skin. Blushing is usually an expression of shame, and itching is a sign of impatience. The body surface is also the somatic locus of exhibitionism. Reflex changes in the skin, such as pallor and flushing, are constituent parts of the emotional states of rage and fear. The skin functions as an important sensory organ and is affected by conversion symptoms such as anesthesia and paresthesia. Clinical studies of skin manifestations as a part of neurotic symptomatology have been conducted onneurodermatitis, eczema, angioneurotic edema, uticaria, and pruritis. Ineczema and neurodermatitis, sadomasochistic and exhibitionistic trend shave been claimed to be correlated with the skin symptoms (Alexander &Flagg, 1965; Engels, 1983, 1985; Torch & Bishop, 1981).
All psychosomatic disorders serve a purpose, such as gaining affection or escaping from responsibilities. Psychosomatic disorders require visibility,and the skin is a choice location for visibility. The need to be seen and to get attention is well served by skin diseases, and with the exception of clearly organic cases, most skin diseases are psychosomatic.Psychosomatic disorders are often associated with self-directed harmful behavior. Self-induced pain and accident-proneness are usually of psychosomatic origin. In skin diseases, scratching is of considerable etiological significance. Psychoanalytic studies imply that scratching is dueto inhibited hostile impulses, which, because of guilt feelings, are deflected from their original target and are turned against oneself. Craving for physical signs of affection, such as being held, cuddled, stroked, and soothed,is involved in skin reactions to the feelings of guilt for being over demanding.Scratching is used as a self-punishing defense mechanism (Alexander,1950; Musaph, 1964, 1977).
Allergies have been defined as an II overreaction" of the organism's defense system. Usually, the body fights antigens (the foreign invading bodies) by producing antibodies, but in allergies, the development of antibodies in reaction to allergens is excessive and definitely out of proportion to the threat.
Allergies represent a combination of physicochemical and psychological determinants. The invading allergens can affect the gastrointestinal system, the respiratory system, and the skin. Allergic disorders vary from mild to very severe, and even lethal. Well over 10% of the U.S. population has some allergy, and one need not exclude the possibility of there being certain genetic predispositions to allergies.
Most probably, the "hammer-and-anvil" scheme mentioned in Chapter15 applies to allergies. The genetic predisposition of the immune systemis the anvil, and the two hammers are the allergens and the stressors. Parental rejection is a highly relevant emotional "hammer" in asthma; frustrations and the loss of a beloved. person are relevant "hammers" in neurodermatitis;and the emotional inconsistency of a child's parents plays the role of "hammer" in infantile eczema.