Blood spots on the arms, a condition called purpura, may be the result of congenital disorders, weak blood vessels, a vitamin C deficiency, steroid use or inflamed blood vessels, according to Healthline. Other causes include bloodstream infections, disorders of the immune system, platelet inhibiting medications and blood transfusions.
Blood spots occur when blood vessels burst under the skin. Purpura is either nonthrombocytopenic, which indicates normal blood platelet counts, or thrombocytopenic, which indicates a lower than normal blood count, explains Healthline. Aspirin, blood thinners and sepsis cause blood spots. Bleeding or clotting disorders, such as lupus, cirrhosis and leukemia, and vitamin B12, K and folic acid deficiencies also cause blood spots, notes Norris Cotton Cancer Center.
Treatment for blood spots depend on the cause, and doctors use skin biopsies and tests that measure blood and platelet count to help determine what is causing the blood spots and whether a serious condition is the culprit, reports Healthline. Coagulation tests and bone marrow biopsies are additional tests doctors may use to help diagnose the cause of blood spots, adds MedlinePlus. If a patient's skin suddenly starts bleeding for an unknown reason or if the blood spot shows no sign of healing, medical attention is recommended.