When skin is blanched, it takes on a whitish appearance as
blood flow
Hemodynamics or haemodynamics are the dynamics of blood flow. The circulatory system is controlled by homeostatic mechanisms of autoregulation, just as hydraulic circuits are controlled by control systems. The hemodynamic response continuously m ...
to the region is prevented. This occurs during and is the basis of the physiologic test known as
diascopy
Diascopy is a test for blanchability performed by applying pressure with a finger or glass slide and observing color changes.Marks, James G; Miller, Jeffery (2006). ''Lookingbill and Marks' Principles of Dermatology'' (4th ed.). Elsevier Inc. Page ...
.
Blanching of the fingers is also one of the most clinically evident signs of
Raynaud's phenomenon
Raynaud syndrome, also known as Raynaud's phenomenon, eponymously named after the physician Auguste Gabriel Maurice Raynaud, who first described it in his doctoral thesis in 1862, is a medical condition in which the spasm of small arteries cau ...
.
Blanching is prevented in
gangrene
Gangrene is a type of tissue death caused by a lack of blood supply. Symptoms may include a change in skin color to red or black, numbness, swelling, pain, skin breakdown, and coolness. The feet and hands are most commonly affected. If the ga ...
as the red blood corpuscles are extravasated and impart red color to the gangrenous part.
See also
*
Diascopy
Diascopy is a test for blanchability performed by applying pressure with a finger or glass slide and observing color changes.Marks, James G; Miller, Jeffery (2006). ''Lookingbill and Marks' Principles of Dermatology'' (4th ed.). Elsevier Inc. Page ...
*
Pallor
Pallor is a pale color of the skin that can be caused by illness, emotional shock or stress, stimulant use, or anemia, and is the result of a reduced amount of oxyhaemoglobin and may also be visible as pallor of the conjunctivae of the eyes o ...
References
Dermatologic terminology
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