Appearance
Wheals (raised areas surrounded by a red base) from urticaria can appear anywhere on the surface of the skin. Whether the trigger is allergic or not, a complex release of inflammatory mediators, including histamine from cutaneous mast cells, results in fluid leakage from superficial blood vessels. Wheals may be pinpoint in size, or several inches in diameter.
Angioedema is a related condition (also from allergic and nonallergic causes), though fluid leakage is from much deeper blood vessels in the subcutaneous or submucosal layers. Individual hives that are painful, last more than 24 hours, or leave a bruise as they heal are more likely to be a more serious condition called urticarial vasculitis. Hives caused by stroking the skin (often linear in appearance) are due to a benign condition called dermatographic urticaria.
Read more about this topic: Acute Urticaria
Famous quotes containing the word appearance:
“The true, prescriptive artist strives after artistic truth; the lawless artist, following blind instinct, after an appearance of naturalness. The one leads to the highest peaks of art, the other to its lowest depths.”
—Johann Wolfgang Von Goethe (1749–1832)
“Our new Constitution is now established, and has an appearance that promises permanency; but in this world nothing can be said to be certain, except death and taxes.”
—Benjamin Franklin (1706–1790)
“Though an unpleasant sort of person, and even a queer threatener withal, yet, if one meets him, one must get along with him as one can; for his ignorance is extreme. And what under heaven indeed should such a phantasm as Death know, for all that the Appearance tacitly claims to be somebody that knows much?”
—Herman Melville (1819–1891)