High platelet count in children is mainly considered to be caused by the following diseases. Firstly, children with Kawasaki disease can be considered to have a high platelet count in the blood, accompanied by persistent high fever, swollen lymph nodes in the neck, prune tongue, and even dilated coronary arteries. Secondly, children with allergic purpura can be considered to have symptoms caused by allergic purpura. Allergic purpura can also cause hypercoagulability in the body, resulting in high platelet count in the blood, which can be promptly treated with anticoagulant therapy, such as dipyridamole. Furthermore infection can also cause hypercoagulable state, and finally other diseases can be considered, such as blood diseases, immune diseases, it is recommended to seek medical attention in time.