Why is my child getting constipated?

Here are the likely possibilities:

Eating too many low-fiber foods. If your child eats lots of milk, cheese, yogurt, or peanut butter, for instance, and not enough fruits, vegetables, and whole grains, he could wind up constipated.

Toilet anxiety. If your child is feeling pressured about toilet training, he might start deliberately withholding his stools. If he shows all the signs of straining to have a bowel movement — stiffening his body, arching his back, and getting red in the face — but nothing comes out, he may actually be trying to hold it in.

Even if your child is potty-trained, he may not be taking enough time on the toilet to completely empty his bowels. That can lead to a buildup of feces that causes the colon to stretch and cramp. An enlarged colon can lead to hard, larger-than-normal, difficult-to-pass stools, making your child even more reluctant to use the potty.

Dehydration. If your child isn't getting enough liquids, his system will respond by absorbing more fluid from whatever he eats or drinks — and from the waste in his bowels, as well. The result can be hard, dry bowel movements that are difficult to pass.

Lack of activity. Movement helps blood flow to your child's digestive system, so if he's not active, he may experience trouble in the BM department.