The terms “acute urticaria” and “chronic urticaria” are misleading because they imply that the hives themselves are acute or chronic, whereas in actuality hives in so-called acute and chronic urticaria not only last about the same amount of time, i.e., hours, but they are indistinguishable morphologically from one another. What then are acute urticaria and chronic urticaria, and do these designations have autnehticity?
By convention, if lesions of urticaria come and go for longer than a span of 6 weeks, the urticaria is considered to be chronic; if, however, those lesions wax and wane for a period of less than 6 weeks, the urticaria is judged to be acute. Whence did the number 6 derive? There is no basis for it whatever. It is arbitrary and makes no sense. Most persons who develop urticaria, whether consequent to such allergens as inhalants, ingestants, injectants, or infestations; from injection into the skin of nonallergenic substances, for example, histamine and 48/80; or from physical factors, such as cold, heat, UV light, or pressure, suffer from hives for a few hours only, at most for only a few days. If one were to divide urticaria, arbitrarily equally but more reasonably, into acute and chronic types, the division would be nearer to 48 hours than to 6 weeks.
A specific cause of urticaria practically never is found when hives have come and gone for a period of weeks, months, or years. In fact, no cause usually is discovered by physicians for hives that disappear completely in hours, never to return. The best chance for identifying the cause of urticaria lies with patients; sometimes they know the answer.
Hives are more or less the same morphologically, i.e., clinically and histopathologically, irrespective of their cause. Clinically, they are wheals, i.e., edematous papules with a pseudopod-like periphery, and, histopathologically, they are characterized by superficial, or superficial and deep, perivascular and interstitial mixed-cell infiltrates. Lymphocytes, neutrophils, and eosinophils are positioned around venules, and neutrophils and eosinophils are scattered among collagen bundles in the reticular dermis. The epidermis is unaffected in a lesion of urtica, and no edema, as evidenced by pallor, is detectable in the papillary dermis of it. The reason is that edema in urtica resides mostly in the reticular dermis, and it cannot be recognized because bundles of collagen present normally there are already separated from one another, in part by fluid of a fixative such as formalin. The findings just described are specific to urtica of all types and of all causes.
A reader should not be perplexed by the words “urticaria” and “urtica.” The former consists of individual lesions of the latter, i.e., the condition itself is urticaria and each of the lesions that constitute it is urtica.
In sum, hives, whether allergic or nonallergic in cause, have similar attributes clinical and histopathologic. Diagnosis of a specific type of urticaria cannot be made on histopathologic grounds alone. Sometimes the cause of urticaria may be inferred by clues clinical, e.g., pressure urticaria on soles, solar urticaria on sites of UV exposure, and cold urticaria limited to lips or oral mucous membranes when a popsicle is the offender. The illogical division of urticaria into acute and chronic types based on temporal considerations does not enhance understanding of the condition in general or of specific types in particular. There is no need for such division, and the sooner it is abandoned the better. The diagnosis should be urticaria, and a reasonable attempt should be undertaken to find the cause of it. If in that endeavor history fails, it is highly unlikely that prick tests for inhalant allergens, patch tests for contact allergens, serologic studies of blood, search for a focus of infection, elimination of particular foods and food additives from the diet, or provocation by particular foods and additives will succeed.
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