Gastroesophageal Reflux Disease (GERD): This is a common condition in infants and young children, characterized by the reflux of stomach contents into the esophagus, leading to vomiting. The symptoms often peak around 4-6 months of age but can start as early as one month.

Viral Gastroenteritis: Common in children, this condition is caused by viruses such as rotavirus, norovirus, and adenovirus, leading to vomiting, diarrhea, and sometimes fever.
Food Allergy or Intolerance: Allergies to milk proteins or other foods can cause vomiting in infants. Lactose intolerance, though less common in infants, can also lead to similar symptoms.
Pyloric Stenosis: A condition where the pylorus (the passage between the stomach and small intestine) thickens, causing projectile vomiting. It typically presents in infants around 2-8 weeks of age.

Intussusception: A serious condition where a part of the intestine slides into an adjacent part, potentially cutting off blood flow. It's a medical emergency and can present with vomiting, abdominal pain, and bloody stools.
Appendicitis: Though less common in very young children, appendicitis can occur and is a surgical emergency. Symptoms may include vomiting, fever, and abdominal pain.
Inborn Errors of Metabolism: Certain metabolic disorders can present with vomiting, among other symptoms, and are critical to diagnose early for proper management.

Congenital Anomalies of the Gastrointestinal Tract: Conditions such as esophageal atresia, tracheoesophageal fistula, or intestinal malrotation can cause vomiting and are usually diagnosed early in life.
Increased Intracranial Pressure: Conditions affecting the brain, such as hydrocephalus or brain tumors, can cause vomiting, especially in the morning, due to increased intracranial pressure.
Adrenal Insufficiency: A rare condition where the adrenal glands do not produce enough hormones, which can lead to vomiting among other symptoms like fatigue and weight loss.