The usual limited number of CT exams (e.g., 1-2 per year), or 2-3 in a short period of time due to illness, are not significantly harmful. Excessive CT examinations can have some potential harmful effects on the body, including gene mutation and killing of white blood cells. 1. Genetic mutation: The working principle of CT examination is X-ray imaging, and the human body is often exposed to X-ray radiation, which will easily cause damage to the human genes, eyes, thyroid gland, blood system and reproductive system, and may cause mutation of the genes of certain organs, and then cause cancer. 2. Killing white blood cells: X-ray radiation will cause a large number of white blood cells to be killed, which will then lead to a decline in the body’s immunity, easily leading to the emergence of various infectious diseases, which may lead to damage to the reproductive system, affecting the fertility of the human body, and causing serious consequences such as infertility or fetal malformation. Therefore, it is recommended that CT examinations must be strictly controlled and performed in accordance with medical advice.