Most colds are caused by bacterial or viral infections, which can cause varying degrees of platelet reduction. The mechanisms that cause platelet reduction are as follows: 1. Some viruses or bacterial toxins, which can directly invade the bone marrow, leading to disorders in the maturation of polymeric megakaryocytes, causing a decrease in platelet production; 2. Causing disorders in the immune mechanism, leading to the destruction of the immune mechanism. After the pathogenic microorganisms invade into the body, they can bind with the receptors of platelets, forming immune complexes, which are recognized and cleared by immune cells and immune system, leading to platelet reduction; 3. The toxins produced by viruses and bacteria can directly cause the aggregation of platelets in the circulation, which can form part of the thrombus and be destroyed when passing through the tiny blood vessels.