1. The pillow is too high: the pillow is not only uncomfortable to sleep, but also may make the normal shape of the cervical spine become bent, causing serious damage to the cervical spine, resulting in muscle fatigue injury and ligament strain or overwork damage, and some accompanying diseases, which are more likely to cause neck and shoulder damage, hand numbness, dizziness and other problems.

3. The pillow is soft or hard: When the pillow is hard, the contact point between the head and the pillow will become smaller, unable to support the weight of the head, and will make the head feel very uncomfortable. When the pillow is too soft, although it will be very comfortable for people to pillow, it cannot continue to maintain a fixed height, and the neck muscles will be easily injured after a long time, which cannot ensure the quality of sleep, and will also affect the normal circulation of cervical spine and blood.