The reasons why one hundred day old babies are very noisy include improper care, teething, intestinal cramps, and neurodevelopmental insufficiency. 1. Improper care: one hundred days of the baby’s body is relatively fragile, need to be carefully cared for. If life, there is not timely feeding, diapers are not changed in time and other issues, it is easy to make the baby feel uncomfortable, and then cry. 2. Teething: Some 100-day-old babies are very noisy, may be caused by teething. Because during teething, the localization will be swollen and painful, causing the baby to be irritable and show the phenomenon of crying. 3. Intestinal spasms: when the baby eats too much, or the temperature of the milk powder is low, it may irritate the gastrointestinal tract, and intestinal spasms will occur, producing pain, which will also cause the baby to cry continuously. 4. Incomplete neurodevelopment: The neurodevelopment of one hundred day old babies is not yet complete, and they will be more excited at night, so they will cry frequently. But this situation will usually disappear with the sound development of the nerves, so do not worry too much. One hundred days of the baby is very noisy may also have other reasons, it is recommended to go to the hospital in time to improve the examination to clarify the cause of the disease, under the guidance of the doctor to give targeted treatment or treatment.