Why is my baby's mouth turning purple?

A baby's purple lips may be caused by various factors, including environmental stimuli, genetic factors, anemia, poisoning, asthma, congenital heart disease, severe pneumonia, or food poisoning. Cold environments can cause blood vessel constriction, while genetic factors may naturally result in darker lips. Anemia and poisoning can impair oxygen supply in the blood, and asthma may lead to hypoxia. If a baby consistently shows this symptom, prompt medical attention is recommended.