Atopic dermatitis is the cutaneous component of a complex hereditary predisposition that also includes a tendency toward bronchial asthma and immediate type I allergy to a range of environmental antigens manifest by allergic conjunctivitis. The linkage among the three is poorly understood but with careful history taking, 75 to 80% of patients are found to have a positive family history.
Atopic dermatitis is a multifaceted problem and exhibits diverse physiological defects, which continue to lead investigators in many different directions. Among the more prominent features, there is evidence of a functioning, but disordered, immune system that overreacts through humoral mechanisms to common environmental antigens (pollen, danders, foods, house dust), while responses of the delayed or cellular immune system to certain antigens (toxicodendron, candida, tuberculin, and some viruses) are depressed. This defect of immune modulation is clinically manifest by abnormal handling of certain otherwise minor infections. Other features include inherently dry skin, altered vasomotor responses, and disturbed sweating with sweat retention.
It is beyond the scope of this book to discuss the complex interactions in atopic dermatitis, but the practitioner must be aware of their existence, as they can be important in the recognition and treatment of certain cases.
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