The causes of red dots on the body may be allergic reaction, allergic purpura, spider nevus and so on. 1. Allergic reaction: the human body can have an immune reaction when exposed to certain sensitizing substances, and the skin system can manifest as itching, erythema, papules, and wind bumps, etc. There may also be other symptoms such as nausea, vomiting, abdominal pain, and diarrhea. 2. Henochromatosis purpura: Henochromatosis purpura is a kind of subcutaneous hemorrhage caused by capillary vasculitis resulting in red blood cells exuding from blood vessels to the skin and mucous membranes. Clinical manifestations include petechiae or ecchymosis of varying sizes, mainly on the lower limbs, with unequal distribution and no discoloration under pressure, and no pain. 3. Spider nevus: the occurrence of spider nevus may be related to the increase of estrogen level, the clinical manifestation of small red spots on the skin, the center protrudes, and extends out to the surrounding area with many spider leg-like capillaries, which often occurs in the neck, face and other parts of the body. It may also be caused by other reasons, and patients are advised to go to the hospital in time.