Causes

Constipation most commonly occurs when waste or stool moves too slowly through the digestive tract, causing the stool to become hard and dry.

Many factors can contribute to constipation in children, including:

• Withholding. Your child may ignore the urge to have a bowel movement because he or she is afraid of the toilet or doesn't want to take a break from play. Some children withhold when they're away from home because they're uncomfortable using public toilets.

  Painful bowel movements caused by large, hard stools also may lead to withholding. If it hurts to poop, your child may try to avoid a repeat of the distressing experience.

• Toilet training issues. If you begin toilet training too soon, your child may rebel and hold in stool. If toilet training becomes a battle of wills, a voluntary decision to ignore the urge to poop can quickly become an involuntary habit that's tough to change.
• Changes in diet. Not enough fiber-rich fruits and vegetables or fluid in your child's diet may cause constipation. One of the more common times for children to become constipated is when they're switching from an all-liquid diet to one that includes solid foods.
• Changes in routine. Any changes in your child's routine — such as travel, hot weather or stress — can affect bowel function. Children are also more likely to experience constipation when they first start school outside of the home.
• Medications. Certain antidepressants and various other drugs can contribute to constipation.
• Cow's milk allergy. An allergy to cow's milk or consuming too many dairy products (cheese and cow's milk) sometimes leads to constipation.
• Family history. Children who have family members who have experienced constipation are more likely to develop constipation. This may be due to shared genetic or environmental factors.
• Medical conditions. Rarely, constipation in children indicates an anatomic malformation, a metabolic or digestive system problem, or another underlying condition.