Anal Fissure: This is a common cause of rectal bleeding in infants, often due to the passage of hard stools. The pain associated with an anal fissure can lead to further stool withholding, creating a vicious cycle.

Allergic Colitis: This condition is often associated with cow's milk protein allergy and can cause blood in the stool. It's a common issue in infants who are formula-fed or have been introduced to cow's milk products.
Gastrointestinal Infection: Viral or bacterial infections can cause inflammation and bleeding in the gastrointestinal tract, leading to blood in the stool.
Intussusception: Although more common in older infants, intussusception can occur in 6-month-olds and is characterized by the telescoping of one portion of the intestine into another, leading to bowel obstruction and potentially bloody stools.

Intestinal Intussusception: As mentioned, this condition requires prompt diagnosis and treatment to prevent complications such as bowel ischemia and necrosis.
Meckel's Diverticulum: A congenital anomaly of the small intestine that can cause significant bleeding due to the presence of ectopic gastric mucosa.
Hirschsprung's Disease: A condition characterized by the absence of ganglion cells in the distal bowel, leading to obstruction and potentially bloody stools.

Juvenile Polyposis Syndrome: A rare condition characterized by the presence of multiple polyps in the gastrointestinal tract, which can cause bleeding.
Inflammatory Bowel Disease (IBD): Conditions like Crohn's disease and ulcerative colitis are rare in infants but can present with bloody stools among other symptoms.
Vascular Malformations: Rare congenital anomalies of the blood vessels within the gastrointestinal tract that can cause bleeding.