Changes in human tissues following radiation exposure are collectively referred to as radiation reactions. If strictly distinguished, they can be divided into radiation reactions that can be repaired and radiation damage that cannot be repaired because of the heavy impact. Generally speaking, radiation reactions are allowed and often unavoidable during radiotherapy. Radiation reactions do not have a significant impact on the patient’s function and are not life-threatening. However, radiation damage is not allowed to occur in most cases, such as paraplegia due to radiation myelitis; necrosis of brain, lung, bone and intestine, etc. These complications not only bring great pain to the patient, but in serious cases even endanger the patient’s life. Radiation reactions can be divided into systemic radiation reactions and local radiation reactions from a broad perspective. I. Systemic radiation reaction (a) the main manifestations of systemic radiation reaction Digestive system: loss of appetite, nausea, vomiting epigastric discomfort. Blood system: decrease in white blood cell count. Other systems: fatigue, headache, vertigo. (2) Factors affecting the whole body radiation reaction 1.Dose The higher the dose, the heavier the reaction. At the same dose, the shorter the time, the heavier the reaction. 2.Irradiation area The larger the irradiation area, the heavier the reaction. 3.Irradiation site Upper abdomen irradiation is most likely to cause whole body radiation reaction, and limb irradiation rarely causes whole body radiation reaction. 4, the radiation energy is high, the action area is deep, and the reaction caused is heavy. 5, the gas pedal’s electron ray action shallow rarely cause whole body reaction. Machine structure: machine protection screen, shielding is not perfect leakage of more rays, the whole body impact is obvious, it is easy to cause a whole-body radiation reaction. 6, individual differences Individual patients are very sensitive to radiation, a very small dose can cause a heavy reaction. However, some people are conditioned reflexes, and can cause nausea and vomiting when comfort treatment is administered to them. Local radiation reaction is the cytological and functional changes caused by the irradiation of certain tissues and organs. (a) Skin and subcutaneous tissue The reaction of radiation on the skin first appears as erythema, local itching or burning sensation. Gradually, hyperpigmentation, dry skin, bran-like flaking, and sweat hair loss leave dilated pores. Hair loss can occur temporarily or permanently depending on the dose. If the dose of skin is too high, it will develop from hyperemia to edema, and even form blisters and then break down, and if the dermis is involved, it will form a radioactive ulcer, which is difficult to heal. At normal doses, several painless peels occur within a few months after the end of treatment, and most of the skin regains its normal color, but with no local sweating and a slightly higher temperature. In the advanced stage, due to the proliferation of fibrous tissue, the subcutaneous tissue within the irradiation area becomes hard and should not be mistaken for cancer recurrence. (ii) Bone marrow The bone marrow hematopoietic system is very sensitive to radiation, in which the red blood cell system is slightly inferior to the bone marrow cells. The function is more difficult to recover than the morphology. Leukopenia is common in the radiation dose range, but aplastic anemia is rare. (iii) Bone The developing bone is most susceptible to radiation effects, mainly manifested as bone growth disorders, such as early healing of the epiphysis and epiphysis. High doses of radiation can also lead to osteonecrosis or radiation osteomyelitis. (iv) Lung Early radiation pneumonia, clinical manifestations of chest pain, cough, less sputum. In the late stage, fibrous proliferation may occur. If it continues to develop, it often leads to symptoms of right heart failure, which is life-threatening in severe cases. (v) Gastrointestinal (GI) After irradiation, gastric dysfunction first appears, such as pyloric spasm and increased peristalsis, which will change to weakness, inhibition of secretion and sputum within a short period of time. High-dose irradiation can lead to ulcer formation and even perforation. The effects of radiation on the small intestine are more significant than those on the stomach and colon, resulting in congestion, edema, and secondary infections, and ulcers and even perforations can be formed with large exposures. Chronic diarrhea and malnutrition are caused by long-term malabsorption in the small intestine. Irradiation of the lower abdomen often causes proctitis or ulcer formation, scar contraction, narrowing and hardening of the lumen, clinical manifestations of constipation, abdominal distension. (vi) Reproductive system A very small dose can reduce the size of the testes and cause sperm scarcity or disappearance. Mature sperm are extremely tolerant to radiation. The hormone-producing testicular mesenchyme is also more tolerant to radiation, but sperm production may be impaired, while sexual performance is not significantly affected. Sexual performance is only altered at high radiation doses. The follicles of the ovaries are extremely sensitive to radiation and can be temporarily sterilized at small doses, because the mature eggs are more tolerant to radiation, so the effect is delayed. The effect is delayed, i.e., menstruation may still occur once or twice after irradiation, and only afterwards does menstruation become suspended. It usually lasts from several months to several years. The initial cycle of menstrual resumption is often irregular. During menopause, sexual desire is maintained in most patients because ovarian function is not destroyed. If the dose is too large (more than 3 Gy at a time), ovulation and ovarian hormone secretion are completely destroyed and the libido disappears. (vii) Salivary glands After irradiation, the salivary glands initially increase in saliva, but soon afterwards, saliva decreases and becomes sticky. The patient’s mouth becomes dry and unbearable, affecting eating. The gland is destroyed by high dose irradiation and replaced by fibrous tissue. (viii) Spinal cord Radiation myelitis is a serious complication that can cause paraplegia and even endanger life in severe cases. Damage to the upper segment is more pronounced than damage to the lower segment. The onset of the disease is closely related to the extent, duration, dose and use of sensitizing drugs. The clinical manifestations of radiation myelitis are of the following types: 1. Transient radiation myelitis: often called Lhermitte’s disease. The disease occurs mostly 1-4 months after radiotherapy. Its typical symptoms: When the patient lowers his head, there is a feeling of electric shock in both lower limbs. There are no positive neurological signs. The above symptoms may subside on their own after a few months. 2.Chronic radiation myelitis is slow to develop, with initial abnormal sensation in the lower extremities, followed by weakness or even paralysis of the lower extremities, urinary and fecal incontinence, and the symptoms may gradually expand upward. 3. Acute radiation myelitis has similar symptoms to chronic, develops rapidly, and can lead to death quickly. There is no effective treatment for radiation osteomyelitis, but prevention is the main thing.