If a small red dot appears on the back of the foot, without pain or itching, it could be allergic purpura, because the allergic purpura produced in this area may only appear as a small red dot, the small red dot is the phenomenon of subcutaneous bleeding, mainly due to allergic factors that cause the skin capillaries in the back of the foot to rupture, or cause localized spotting bleeding. The formation of this phenomenon in the area may also be the patient’s eczema, although eczema for many people with itchy symptoms, but there are some people due to individual differences, after the production of eczema itching may not be too obvious, eczema once produced, may form an inflammatory papule, which will also be seen from the appearance of small red dots.