A petechia constitutes small red to purple-colored spots that most frequently appear on the skin but can also manifest on the surface of certain organs or on the lining of certain cavities, such as that of the bladder. These spots are secondary to small hemorrhages. Petechiae are also symptoms of different diseases, such as infections or allergic reactions, but are above all associated with purpura, a disease that induces these lesions visible under the skin due to extravasation, the process of blood leaking out from the capillaries lying just under the skin. Petechiae constitute the smallest form of these purpuric lesions. The main characteristic of these petechiae and all purpuric lesions is that they do not disappear when pressure is applied.