Stool tests are necessary.
Thank you for the query.
which lasts longer than 48 hours needs to be checked with stool tests. Diet is not the reason of his symptoms so BRAT diet
His problem may be caused by bacterial infection (most common reason) or due some more serious issues like inflammatory bowels disease.
Inflammatory bowels disease is more possible if he has also vomiting
with cramps, weight loss
, blood and mucus in stool.
Please consult gastrologist. Stool test and stool culture test should be done at first. Antibiotic is necessary. If it wont help or give any answer, colonoscopy
should be done.
Hope this will help. Feel free to ask further questions.