Teething: This is the most common cause of drooling in infants around this age. As teeth begin to erupt, it stimulates the production of more saliva, and the infant's ability to swallow and manage this excess saliva is still developing.

Normal variation in infant development: Some infants simply produce more saliva than others, and this can be a normal variation without any underlying pathology.
Gastroesophageal reflux disease (GERD): Infants with GERD may drool more due to the discomfort and the body's attempt to protect the esophagus from acid.
Oral motor issues: Difficulty with oral motor coordination can lead to problems with swallowing and thus result in drooling.

Pyloric stenosis: Although less common, pyloric stenosis can cause projectile vomiting, which might be preceded by drooling due to the buildup of saliva and food. It's crucial to diagnose early as it requires surgical intervention.
Esophageal atresia or tracheoesophageal fistula: These congenital anomalies can lead to drooling due to the inability to swallow properly. Early diagnosis is critical for surgical correction.
Neurological disorders: Conditions such as cerebral palsy or other neurodevelopmental disorders can affect the muscles used for swallowing, leading to drooling.

Congenital syphilis: A rare condition that can cause a variety of symptoms, including drooling, due to the infection affecting the development of the fetus.
Tuberculosis: Although rare in infants, TB can cause a range of symptoms including drooling, especially if it affects the gastrointestinal tract or the central nervous system.
Neurodegenerative disorders: Certain rare neurodegenerative disorders can present with drooling among other symptoms, due to the progressive deterioration of neurological function.