A non-blanching rash (NBR) is a skin rash that does not fade when pressed with, and viewed through, a glass.
It is a characteristic of both purpuric and petechial rashes.[1] Individual purpura measure 3–10 mm (0.3–1 cm, 3⁄32-3⁄8 in), whereas petechiae measure less than 3 mm.[2]