The baby's lips turn blue when crying, but return to normal shortly afterward.

When a baby cries and their lips turn purple, then return to normal shortly afterward, it could be due to physiological factors or pathological causes such as respiratory diseases or congenital heart disease.

I. Physiological Factors

During intense crying, a baby's airway resistance increases, leading to elevated pressure in the lungs and particularly within the body's capillaries and arteries. Since babies have delicate skin rich in capillary and venous networks, increased venous pressure can cause temporary dilation of capillaries or veins. This may result in cyanosis—bluish or purplish discoloration of the lips—which is considered a normal physiological phenomenon.

II. Pathological Factors

1. Respiratory Diseases

If a baby has airway narrowing or space-occupying lesions in the respiratory tract, crying may lead to oxygen deficiency, causing the lips to turn purple. Under medical guidance, medications such as compound pholcodine oral solution or procaterol hydrochloride oral solution may be used for treatment.

2. Congenital Heart Disease

In some babies, lip cyanosis during crying may be caused by congenital heart defects, such as atrial septal defect or ventricular septal defect. Prompt medical evaluation is necessary, and treatment under a doctor’s supervision—such as cardiac surgery or interventional procedures—may be required.

Additionally, seizures such as those caused by epilepsy could also lead to such symptoms; prompt comfort and calming of the baby are essential during an episode.