Wheal
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A wheal is a firm, elevated, rounded or flat toppedGoldman and Ausiello. Cecil Textbook of Medicine. Saunders. 2003. Page 2451. ISBN 072169652X., generally pale red papule or plaque, that is transient, typically disappearing within 24-48Stephen and Longo. Harrisons Principles of Internal Medicine, 15th Edition. McGraw-Hill Professional Publishing. 2001. Pages 95, 306. ISBN 0070072728. hours; a lesion that is well demarcated, and may be round, oval, gyrate, annular or irregular/serpiginous with pseudopods. This dermatologic finding is due to the infiltration of edema into the papillary body of the dermis. Therefore, while the borders are sharp, they are not stable, and as this short-lived papillary edema shifts, each wheal transiently movesHabif, Thomas P. Clinical Dermatology: A Color Guide to Diagnosis and Therapy. Mosby, Inc. 2004. Page 825. ISBN 0323013198. from involved to adjacent uninvolved areas over a period of hours. Also note, while this finding is usually pale red, if the amount of edema is adequate to compresses superficial vessels, the wheal may have a white center.Fitzpatrick, Thomas B, et al. Dermatology in General Medicine. McGraw-Hill. 1986. Pages 29-30. ISBN 9780070796898. The epidermis is not affected and there is no scaling. A rash consisting of wheals may be called a uticarial exanthem, or urticaria, and may be an allergic response to innumerable initiating agents such as drugs or insect bites. Wheals may also be produced with Dariers sign, and by stroking the skin of certain normal persons who demonstrate the phenomenon called dermatographism.
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