The 4.5 month old baby can’t sleep well, may be caused by poor environment, or vitamin D deficiency, pediatric eczema and other diseases. 1. poor environment: when the 4.5 month old baby in the temperature is too high, too low environment to sleep, it is easy to sleep, if there is no other abnormalities, is a normal physiological phenomenon. 2. Vitamin D deficiency: The common causes of this disease are insufficient sunlight, insufficient intake or synthesis of vitamin D, and factors related to living indoors for a long time. Affected children will wake up at night, irritability, excessive sweating and other symptoms, so there is a lack of sleep. 3. Pediatric eczema: the cause of this disease is more complex, studies show that it is related to heredity, poor skin barrier function, contact with allergens and other reasons. Because the affected children will have itchy skin, blisters and other symptoms, so it will lead to the affected children can not sleep soundly, affecting sleep. 4.5 month old baby can not sleep soundly, there may also be other causes, it is recommended to go to the hospital, improve the examination to clarify the cause of the disease, under the guidance of the doctor to give targeted treatment or treatment.