Infants shaking their heads from side to side after falling asleep may be caused by physiological or pathological factors. Physiological factors such as imperfect development of the nervous system and pathological factors such as calcium deficiency and eczema can lead to shaking of the head from side to side after falling asleep. 1. Physiological factors: infants’ nervous system is not well developed and cannot fully control their neuromuscular tissues, so head shaking may occur during sleep; in addition, when infants are in light sleep, head shaking may also occur, and it will usually disappear when they enter deep sleep. 2. Pathological factors: infants with calcium deficiency have elevated excitability of the developing nervous system, which leads to incomplete control of the muscle tissues, thus appearing to be easily provoked and shaking their heads from side to side during sleep; in addition, infants suffering from eczema may feel uncomfortable due to touching the eczema, and thus keep shaking their heads from side to side to alleviate the discomfort. There may be other reasons for babies to shake their heads from side to side after falling asleep. It is recommended to go to the hospital in time, complete the examination to clarify the cause of the disease, and then give targeted treatment or therapy under the guidance of the doctor.