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I am sorry to hear about your son. Since all possible causes of vomiting have been ruled out, there is a possibility that this is cyclical vomiting syndrome. This is characterized by bouts of unexplained vomiting that stop as they came with a symptom free period and start again. There is no test to diagnose it yet. Diagnosis is made by a careful history which shows that each vomiting episode was similar to the previous one in terms of pattern, duration and symptoms.
While this may not have triggers but often triggers are found like emotional stress, exams, fights in schools, inability to adjust to one’s environment etc.
Treatment is supportive with medications to stop vomiting, IV fluids, a calm peaceful environment, counseling of the whole family etc.
The other possibility is worm in stool and acidity. H pylori infection can be another possibility.
It is difficult to comment for sure on net hence discuss this with your son’s doctor. Hope this helps. Please let me know if there is any thing else and do keep me posted. Take care!
Thank you very much! I will talk to the doctor about these possibilities. Then I will let you know.