Wheal 2651744 219714576 2008-06-16T15:24:45Z Fratrep 4541225 Repairing link to disambiguation page - [[Wikipedia:Disambiguation pages with links|You can help!]] {{otheruses}} {{Infobox Symptom | Name = {{PAGENAME}} | Background = | Image = Welt on wrist.jpg | Caption = A welt (wheal) formed on a person's skin after being struck on the neck with a credit card | ICD10 = {{ICD10|L|50|9|l|50}} | ICD9 = {{ICD9|708}} | ICDO = | OMIM = | DiseasesDB = 13606 | MedlinePlus = 000845 | eMedicineSubj = med | eMedicineTopic = 3014 }} A '''wheal''' or '''wheal response''' (also termed a '''welt''') is a firm, elevated, rounded or flat topped,<ref name="Cecil 22">{{cite book |editor=Lee Goldman, Lee; Ausiello, Dennis |title=Cecil textbook of medicine |publisher=W.B. Saunders |location=Philadelphia |year=2004 |edition=22nd ed. |pages=2451 |isbn=0-7216-9652-X |oclc= |doi=}}</ref>, generally pale red [[papule]] or [[plaque]]<ref name="Harrison's 15"/> swellings of the skin. They are usually well demarcated<ref name="Cecil 22" /> and may be round, oval, gyrate, annular<ref name="Harrison's 15"/> or irregular/serpiginous with pseudopods in shape. They often itch or have a burning sensation but are [[transient]], typically disappearing within 24-48 hours.<ref name="Harrison's 15">{{cite book |editor=Braunwald, Eugene; Fauci, Anthony; Kasper, Dennis; Hauser, Stephen; Longo, Dan; Jameson, Larry |title=Harrison's principles of internal medicine |edition=15th Edition |publisher=McGraw-Hill |location=New York |year=2001 |pages=95 & 306 |isbn=0070072728 |oclc= |doi=}}</ref> An itchy rash consisting of wheals may be called a uticarial exanthem, or [[urticaria]], and more commonly as '''hives'''. ==Causes== Wheals are due to fluid build up in the skin as a result of a blow or lash to the [[skin]] as commonly occurs to [[paintball]] players, or an [[allergic reaction]] to innumerable initiating agents such as drugs or insect bites. These cause infiltration of [[edema]] into the papillary body of the [[dermis]]. Wheals may also be produced with [[Darier's sign]], and by stroking the skin of certain normal persons who demonstrate the phenomenon called [[dermatographism]].<ref name="isbn0070796890">{{cite book |editor=Fitzpatrick, Thomas B. ed.|title=Dermatology in general medicine: textbook and atlas |publisher=McGraw-Hill |location=New York |year=1986 |pages=29-30 |isbn=0070796890 |oclc= |doi=}}</ref> Finally they may be formed by the injection of fluid with a [[hypodermic]] syringe. While the borders are sharp, they are not stable, and as this short-lived papillary edema shifts, each wheal transiently moves<ref name="isbn0-323-01319-8">{{cite book |author=Habif, Thomas P. |title=Clinical dermatology: a color guide to diagnosis and therapy |publisher=Mosby |location=St. Louis |year=2004 |pages=825 |isbn=0-323-01319-8 |oclc= |doi=}}</ref> 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.<ref name="isbn0070796890"/> The [[Epidermis (skin)|epidermis]] is not affected and there is no scaling.<ref name="isbn0070796890"/> ==Pathophysiology== {{Unreferencedsection|date=March 2008}} This effect is most likely mediated by Neurokinin 1 activation in response to substance P released during the injury by cutaneous sensory nerve fibers A & C. The result of NK1 activation is plasma leakage, and arteriole dilation, which increases blood flow. ==See also== {{wiktionary|wheal}} <br clear="all"/> ==Footnotes== {{reflist|2}} [[Category: Dermatology]] [[Category:Skin diseases]] {{dermatology-stub}} [[de:Quaddel]] [[pl:Bąbel]] [[ru:Рубец (след от раны)]]