It may be normal for babies to have a crooked mouth when they laugh, but it may also be caused by diseases. Parents are advised to bring their babies to the hospital in time for checkups to confirm the specific causes of the crooked mouth and to carry out targeted treatment. 1. Normal: If it happens only occasionally and not normally, it may be caused by personal expression. Normally, you can massage the muscles around the child’s lips to allow them to develop in a balanced manner. If the symptoms do not disappear, it is necessary to consult a neurologist. 2. Disease: It may also be caused by the baby’s facial neuritis and other disease factors, should pay attention to see if the baby has other symptoms, such as nasolabial folds become shallow, widening of the eye fissure, etc., if the above symptoms, it is possible that the baby is suffering from a disease condition should be to the hospital for further diagnosis and treatment. Parents should pay attention to observe whether the baby often appear a smile on the mouth crooked symptoms, if only occasionally, then do not need to worry too much, if often appear, it is recommended to go to the hospital for examination.