When a child or adult has gluten intolerance, or celiac disease, they tend to have other issues until the gluten problem is solved, like lactose intolerance too. Sometimes the gluten thing is hit or miss. Pasta is a big trigger, sometimes with certain breads you can slide by and get symptoms later. Something in the back of my mind also says soy has some glutamate in it, which has some chemical similarities to gluten. Also, I've recently read that tomatoes have a large amount of glutamate in it. Glutamate also is huge in soy sauce and in MSG products. If you check in a lot of processed foods, the yum factor lies in MSG. Trying to avoid MSG may help you and your kid (though I don't have celiac disease, MSG gives me hideous headaches and migraines these days).
Try looking up celiac disease and you will find what your child can and cannot eat. Corn, potatoes, rice, quinoa, amarynth flour, tapioca, teff, and some other items are perfectly okay with gluten intolerant folks. The best way to eat if you're gluten sensitive is having a lot of fruits, veggies, and lean meats. Some diets that are great are Meditteranean and South Beach - which focus on lean fish and meats and tons of veggies, and not a whole lot of refined flours and sugars. Children need fats and sugars, but not as much as the typical American diet is coming to these days.
With celiac disease, you get a lot of nutritional deficiencies. The first step is to get your child tested and then work on a program so that they have a normal growth pattern and no nutritional problems. Celiac disease has symptoms like the scaly red patches around elbows, buttocks, ears, and sides of nose, and quite often sebbhorrheic dermatitis (big flaky scaly dandruff). Over time, the buttocks of the person looks flat or 'wasted,' what I like to call 'frogbutt.' Also over time, the child looks really cherublike, and has a belly. It's cute at first, but it can be a sign that their intestines are having trouble. Gluten intolerance is an auto-immune issue and gluten pretty much acts like a poison to that person's system. It destroys the vili in the intestestines and over time, makes the vili atrophy and flatten down, making it hard to absorb a good amount of nutrients in food. Most celiacs are very deficient in B-Complex, Magnesium, and Calcium, among other minerals and vitamins.