My son is twelve and experiences abdominal pain and discomfort often usually in the evening or during the night. He usually vomits. This has been happening about every other week for three months. He also has had a rash on his torso that resembles heat rash. His stomach has been finicky since he was little and he vomits easily, but I am noticing the frequency increasing. Does this sound like a food intolerance or allergy?