The sudden appearance of red dots on the body, if they are small, may be caused by capillary bleeding, which is a common type of phenomenon. Some women will have a small amount of capillary rupture bleeding before menstruation, which is usually due to hormone metabolism and is nothing to worry about. If small red dots appear on the lower legs and feet, you may have anaphylactic purpura. There are light types and heavy types of allergic purpura. The light types, where the lesions occur on the skin, can be treated well by taking medication. There are also heavier types of allergic purpura, such as the abdominal type of purpura which is usually associated with intestinal damage and the renal type of purpura which is associated with kidney damage. Therefore, in either case, you should visit a regular hospital for a clear diagnosis by a dermatologist and active treatment to avoid delaying the condition.