Blanchable erytherma is when an area that is red turns white when light pressure is applied to it with fingertips and it returns back to red as soon as the pressure is removed.
This are usually found in bony prominence area.A localized reaction which may due to any of these factors, poor blood circulation, inadequate blood supply to the areas due to pressure or swelling of the affected area. This is called blanchable.
Nonblanchable according to Pressure ulcer Advisory panel ( NPUAP)staging system of 2007 is if redness did not go away after you applied light pressure with fingertips to red areas of the skin.The intact skin in nonblanchable redness of a localized areas and is usually over a bony prominences caused by pressure, shear or friction.This is stage 1 of the staging and may be difficult to find out in dark skin individuals. The color may be different from the other skin and can be painful, cooler than surrounding areas,warm ,soft or firm.(International NPUAP-EPUAP Pressure Ulcer Classification System)