I am sorry to hear about your sons digestive issues. Great job with the keifer! I have heard of probiotics to give babies. I don’t know what a good brand would be and I cant remember where I saw them before. I might have been in an alternative doctors office. Renew life makes a great brand for children but they are chewable tablets. I think they are more for 2 year old and up but you might still want to look into it for later on. I would suggest talking to a doctor before starting anything. I am sure an integrative doctor in your area might know of something that would be good for your son.
Website for children probiotics:
Hope this helps! I think your son has a fantastic father or mother that is willing to do research to make him better 😀