The small pinprick of blood spots on the arm, consider the following possibilities: 1, pigmented purpura dermatosis, this disease is due to small arteries, small veins, capillary intravascular pressure increase, red blood cell extravasation and cause, can appear rust-colored petechiae, petechiae, pressure does not fade. The treatment can be oral vitamin C capsules, calcium carbonate D3 tablets, and topical Denide ointment application. 2. Consider hemangioma, a benign vascular proliferative disease caused by human ageing, which can usually be left untreated. If it affects the aesthetics you can choose laser treatment options for conditioning. 3, allergic purpura, can appear petechiae, petechiae, pressure does not fade, symmetrical distribution. In terms of treatment, you can take oral compound rutin tablets and use topical furnace glycerine lotion.