Diarrhea, swollen belly and gas
Weightloss.
Irritability: feeling very angry and very sad.

It is an allergy to gluten, a protein found in wheat (flour), barley, and rye. The allergy causes inflammation in the intestine and stops it from absorbing nutrients.
You have to do a blood test to know if you have celiac disease.

Celiac disease is a chronic disease, which means there is no way to cure it.
Luckily, there is a lot of research going on today and it is very easy to remove foods that have gluten from your diet. There are many stores that have lots of gluten free foods!