I work with a little boy who recently started the gluten and cassein free diet. His behavior has changed erratically: he has become obsessed with the microwave or any electrical appliance, he cries very easily, he poos more and he seems more spacey. This just happened when he started the diet. What are the side effects of the diet ?
I have been doing the casein free, gluten free, yeast free diet with my son for 10 years now. I also have him on a few supplements. My son is not "cured". He is doing very well, though. I remember when I first started the diet with him, he got really hyped up for a few weeks. His poo also changed. It took a while to kill of the yeastie beasties but then I did begin to see a few improvements. He had better eye contact and his red, rashy cheeks, red ears went away. He became more regular (poo). Now that he is 13, he is very calm. He is a little love. He still can't read or write, but he can tell me that he loves me and tells me allllll about computers. We're happy. Stay patient, give it a go.
I can speak from personal experience as an adult who went gluten and dairy free that it is a big diet change, and needs to be done carefully. I would imagine someone could have changes in stools if they weren't getting the right balance of foods. I've also noticed on some sites that people list "kid-friendly gluten and dairy free foods" and the list had only junk food. So being gluten and dairy free does not automatically mean that the child is getting a healthy diet.
I found the easiest way to think about being gluten and dairy free is to go to simple and natural foods. I eat much more vegetables than I used to, and those are a good source of fiber. Also fruits, meats, nuts, and eggs. I cook with olive oil and canola oil much more often than I used to (have to skip the butter). And there are many options for gluten-free grains that are becoming more readily available, even in main stream stores.
So to answer your question, I could imagine this child might be having a reaction to the change in diet. But it doesn't mean they should give up the diet. They should evaluate what it is that he/she is eating, and perhaps consult with a nutritionist. One meeting with a nutritionist could be enough. Many schools and health clubs have nutritionists now, and physicians might know of people for referrals.
It seems that many complain of worsening symptoms when changing diets. As a microbiologist, this makes sense to me. The chemicals that the "bad" microbes are producing are released en masse when there is whole-scale dying of those microbes because the food they used to eat is no longer available. When the microbe cell dies, it's walls break open and the contents spill out faster than they might be excreted by a live microbial cell. Once the die-off has been completed, the increased symptoms should subside.