Twelve-year-old child sweat odor may be caused by excessive sweating, may also be hyperthyroidism, smelly sweat and other diseases. 1. Excessive sweating: when the twelve-year-old child sweating more after strenuous exercise, did not change the body clothes in time, so that the sweat stays in the skin and clothes for a long time, there will be a sweaty situation, which is a normal phenomenon. 2. Hyperthyroidism: the occurrence of this disease is mainly due to overactive thyroid function, self-synthesis and secretion of thyroid hormone increase and cause, may be excessive iodine intake, thyroid nodules, genetic and other factors. As hyperthyroidism can cause hyperhidrosis, when the body sweats too much, to a certain extent, children are prone to sweaty odor. 3. Odorant Sweat Disorder: The causes of this disease include abnormal secretion function of sweat glands, heredity, abnormal bacterial decomposition, high temperature and so on. The typical symptom of hyperhidrosis is that it emits an irritating odor, especially after exercise, so that the affected children have a heavy sweat odor. If the heavy odor of sweat in a twelve-year-old child is ruled out as a normal phenomenon, it is necessary to go to the hospital in time to clarify the specific cause.