Children with hard bumps on the legs, itching and high fever of 39 to 40 degrees may be related to rubella virus infection, hand, foot and mouth disease and other factors. 1. Rubella virus infection: children may have these symptoms when they have rubella virus infection, which occurs most often in the spring, accompanied by swollen lymph nodes behind the ears and occipital region, which will subside in about 2 to 3 days. 2. Hand, foot and mouth disease: Hand, foot and mouth disease can also cause children to have a high fever, blisters, itching and other conditions accompanied by drooling symptoms. Children with hard lumps on the legs, itchy and high fever of 39 to 40 degrees may have other reasons, it is recommended to go to the hospital in a timely manner to carry out the relevant examination, clear cause of the symptoms of the active treatment.