Unfortunately, constipation is common in the toddler years and any number of foods could set it off. You may wonder if perhaps your toddler or preschooler is drinking too much chocolate milk, causing his inability to go. It is a possibility, but there could be other causes as well. A bit of experimentation will help you find your child's answers.
The Milk or the Chocolate?
Between the milk itself and the chocolate you add, it's more likely that it's the milk causing constipation, as it's known for its binding effect. However, chocolate could be a factor if your child has irritable bowel syndrome.
What's "Too Much"?
Every child is different and your kid may get stopped up for days after having two glasses of chocolate milk, while the neighbor's kid is fine drinking five a day. Note that there are other foods that cause constipation as well, such as bananas, yogurt, cheese and cooked carrots. The problem may not necessarily be that your child is drinking chocolate milk; it's that he's drinking in conjunction with eating other constipating foods. He may be fine if you eliminate one or the other.
Fixing the Problem
Stop giving your child milk for a few days to see if it solves the constipation problem. If she's soon able to go, you'll know you've found the culprit. You can then begin to add a glass in, watching how it affects her. If it doesn't immediately solve the problem, you'll have to restrict her diet even further to get things moving, then add the potentially constipating foods in one at a time to see which ones affect her.
You can also help her constipation problems by increasing liquid intake, either directly or by serving watery foods like fruits, and giving her foods with more fiber.
Alternatives for Calcium
If it turns out that dairy products are constipating your child, you need to look for alternatives for his calcium. Try milk alternatives, like soy or almond milk, particularly those that are fortified. Cereals, juices and tofu can also have calcium. Check the labels if you're not sure.