Under the age of three, the "yin and yang eyes" have weak yang, and they can see things in that world. Some babies cry for no reason, just to see what adults can't see. So don't take the baby to quiet and dark places and places where you do white things to prevent evil spirits.
You can prepare something for your baby to ward off evil spirits.
Adults are full of yang, and dark things can't be close, so they are not afraid of these things.