ABSTRACT
I. Introduction 518
II. Nomenclature 520
III. Clinical Aspects 521
IV. Relationship between Immediate Contact Reactions and Hand Eczema
V. Etiopathogenic Mechanism 523
VI. Causative Agents 526
A. Animal-Derived Proteins 528
B. Vegetable-Derived Proteins 529
C. Enzymes 531
VII. Diagnosis 532
VIII. Concluding Remarks 533
References 534
I. INTRODUCTION
Hand dermatitis is a multifactorial condition with a varied biological and clinical spectrum in which endogenous and exogenous factors are interwoven. Traditionally, contact dermatitis of the hands is regarded as being either allergic or irritant in nature. The distinction is based on the clinical features and patch testing results. If the patch tests are positive and relevant, the particular dermatitis will be classified as allergic. Irritant dermatitis is mainly a diagnosis
by exclusion, since diagnostic tests for irritancy are not available. Allergic hand dermatitis usually means a cell-mediated delayed hypersensitivity reaction to a low-molecular-weight allergen. However, some patients have a different type of hand dermatitis induced by contact, which-although frequently proved to be allergic in nature-usually produces negative results with conventional patch testing. These patients suffer from what appears to be a common irritant or allergic hand dermatitis or an atopic hand dermatitis, but they develop immediate flares characterized by itching, erythema, and sometimes wheals or microvesicles within an hour after contact with certain substances, usually foods such as fish, shellfish, vegetables, and spices.1-14 The patho genesis of this immediate contact dermatitis is still not well known, but presumably constitutes part of the spectrum of the contact urticaria syndrome (CUS) (Table 35.1). CUS, defined as a biological entity in 1975 by Maibach and Johnson,15 comprises a heterogeneous group of inflammatory reactions that generally appear within minutes after contact with the eliciting agent, and disappear within 24 h, usually in a few hours.16-24 The term “syndrome” illustrates their biological and clinical polymorphism. Even though contact urticaria is, largely, an immediate-type reaction, it may also represent one of the pathogenic events in chronic hand eczema. These “immediate” contact reactions are not infrequent in hand dermatitis patients, adding a new dimension to the clinical and pathogenic mechanisms of hand dermatitis.
