Hello, Nutrolin B contains different types of vitamin B and is generally recommended if a child has vitamin B deficiency. In the case of your child, I would mostly make sure the child takes plenty of fluids and oral rehydration solutions to substitute both the water and electrolytes that he looses with diarrhea. The vitamin supplements are important when a child has a deficiency of these vitamins but I would not give these supplements if the child is not deficient in these vitamins. I hope this answers your query and is helpful to you. Let me know if I may assist you further. Regards, Dr. Antoneta Zotaj, General and Family Physician