Commonplace urticaria is a monomorphous eruption of intensely pruritic wheals and is usually of sudden, sometimes explosive onset. Occasionally, victims will note gradual onset with increasing intensity, but this is not the typical presentation. A small number of patients during the acute phase will develop laryngeal or glottic edema, bronchospasm, and circulatory collapse, which can comprise fatal anaphylactic shock. This is a true medical emergency that requires prompt action. Acute urticaria is more frequent in young persons. Chronic hives are more frequent in middle-aged women. Urticarial lesions may also occur in other skin conditions, such as the peribullous areas of pemphigus vulgaris and bullous pemphigoid, or the wheal lesions seen as part of erythema multiforme. Here, however, the welts are associated with other lesions of more distinctive morphology. They are more fixed in duration, and the resemblance to true urticaria is superficial.
At one time or another, urticaria is estimated to affect 15 to 20% of the population. In approximately 95% of these cases, the eruption resolves within a few days or months without sequelae. Urticaria is separated into acute and chronic forms on the basis of duration, with 6 weeks being the most generally accepted point at which chronicity begins. Acute urticaria is frequently the result of an immediate (type I) hypersensitivity reaction or a drug-induced pseudoallergic reaction. Linkage between cause and exposure in acute disease can often be established. Chronic urticaria can persist for years and is a vexing problem for the patient and practitioner. Despite extensive workup and testing, the cause of chronic urticaria is seldom determined. An even less common type is chronic intermittent urticaria, in which symptoms can last for years, but are punctuated by symptom-free periods of varying duration. Causes of intermittent disease parallel acute urticaria, and careful history of periodic or cyclical exposures may reveal the cause.
Discrete wheals develop rapidly on any body location. New hives may develop at one site while they are resolving in others. Lesions that remain fixed at one site longer than 24 to 48 hours' duration suggest another diagnosis.
History-taking for provoking factors in urticaria is tedious and complicated because of the large number of possible etiologies. The factors listed here are among the most common, but this does not represent an exhaustive listing. These will be found more frequently in acute and chronic intermittent urticaria. Despite the low yield in cases of chronic disease, a careful and repeated history must be taken. Provoking factors may cause hives by means of type I (IgE-mediated) hypersensitivity reactions, type III (immune-complex-mediated) hypersensitivity reactions, or by nonimmunologic release of histamine or other mediators. This latter mechanism is referred to as a pseudoallergic reaction. Existing acute, chronic intermittent, or chronic urticaria may also be directly exacerbated by a number of substances that stimulate direct histamine release from mast cells or initiate other mediator cascades. Also, certain substances and activities that promote vasodilation will worsen active hives.
1. Immunologic type I or type III reaction:
Foods: Fish, shellfish (especially oysters and mussels), meats (especially pork and mutton), cheeses that are mold-containing, strawberries, citrus fruits, nuts, seeds, peanuts, tomatoes, chocolate, dairy products (especially milk), egg whites.
Inhalant allergens: Pollens (would be among the more common causes of chronic intermittent urticaria and would cause seasonal exacerbations), tobacco smoke, tobacco additives such as menthol, house dust, airborne molds, and fungi (again often seasonal).
Chronic focus of infection: Dental abscess (usually the patient has poorly maintained dentition on physical exam, with one or more sensitive teeth; however, occult abscess formation without signs or symptoms has also been reported), chronic sinusitis, chronic dermatophytosis, candidiasis, intestinal parasitosis, diverticulitis.
Infectious disease: Hepatitis B, mononucleosis, Coxsackie infections.
Insect bites or stings may provoke attacks of urticaria of varying duration.
2. Substances that cause pseudoallergic urticaria or may exacerbate existing urticaria by direct mediator release:
Foods: Lobster, crayfish, scombroid fish (usually old or improperly processed), strawberries, yeast and yeast-containing cheeses, spinach, chicken livers, red wines, egg whites, tomatoes, tonic water (quinine content).
Food additives: Salicylate derivatives, tartrazine and azo dyes (also widely used in medications, these dyes are listed with each medication in the Physicians' Desk Reference [PDR]), benzoates, sulfites.
Medications: Morphine, codeine, scopolamine, atropine, salicylates, indo-methacin, thiamine, quinine and quinine derivatives, polymyxin B, d-turbocu-rarine, succinylcholine, decamethonium, certain radiographic contrast materials, gallamine, ACTH, dextran, halothane, ACE inhibitors (may provoke angioedema by direct action on the kinin cascade).
3. Diseases reported to provoke urticaria: atopy, systemic lupus, dermatomyositis, lymphoma, dysproteinemias, hyper- and hypothyroidism. With the exception of hyperthyroidism, these are rare associations. Atopy and thyroid disease are associated with common hives while the others are usually associated with urticarial vasculitis, a disease distinct from common hives that will be covered in the differential diagnosis section.
Although antihistamines are readily available over the counter, they are not a problem because they merely suppress but do not alter the disease process.
At the initial visit for acute urticaria, history-taking should focus on the provoking factors previously listed. With ongoing symptoms or when investigating chronic urticaria, an exhaustive review is indicated.
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