what are the blood spots that appear and disappear on my arm
Blood spots. Blood spots under the skin may be either purpura or petechiae. Purpura might look like bruises, but they are not caused by an injury as most regular bruises are. Petechiae don't look like bruises. They are tiny, flat, red or purple spots in the skin, but they are different than the tiny, flat, red spots or birthmarks (hemangiomas) that are present all the time. Sudden unexplained bruising or blood spots under the skin or a sudden increase in the frequency of bruising may be caused by: A medicine, such as aspirin or blood thinners (anticoagulants). Infection that causes the buildup of toxin in the blood or tissues .