When small red dots appear on the knee, the appearance of the red dots needs to be carefully observed to determine how the factors are formed. If it is a red or brown change and does not fade when pressed by hand, consider that it may be a purpura disorder, which is related to bruising caused by increased permeability of subcutaneous capillaries. You can choose to go to the local hospital for routine blood tests to clarify whether it is allergic purpura or thrombocytopenic purpura, and then carry out targeted treatment. If the red spots on the knee with itching and sometimes mildly raised to touch, consider the possibility of erythema and papule-like changes, related to allergic irritation. It is recommended to use Denide cream or Clobetasol Propionate cream, which will soon subside the symptoms. Do not consume too much chili or alcohol or seafood foods during treatment to avoid aggravation of symptoms.