Red dots on the arm like moles may be caused by allergic purpura, spider nevus, cherry angioma and other diseases, patients should seek medical attention in a timely manner to clarify the cause of the disease after treatment. 1.allergic purpura: a kind of metamorphic inflammation of small blood vessels all over the body, related to bacteria, viruses, food, drugs, etc., can lead to the patient’s torso and limbs appearing pinpoint to soybean-sized purpura, partly accompanied by abdominal pain, joint pain, low fever and other symptoms. 2. Spider nevus: red spots on the arm like moles may also be caused by spider nevus due to increased estrogen in the body, mostly seen in patients with cirrhosis of the liver, but also seen in pregnant women or normal people. The skin rash will disappear after pressing, and may subside after active treatment of the original disease. 3. Cherry hemangioma: red dots like nevus on the arm may also be caused by cherry hemangioma, which is more common in middle-aged and old people, and is caused by capillary hyperplasia and dilatation, and usually does not need to be dealt with. If you have a red spot like a mole on your arm, you need to consult a doctor in time to get a clear diagnosis.