Hello Dr, Thank you for asking at HCM. If you have ruled out bacterial and parasitic infections, next thing I would think of will be food allergy. Although he is not on cows milk, he might be exposed to milk proteins from some hidden sources or from breast milk. Or it may be some other food allergy like soy, peanut, tree nuts, egg, fish, shell fish or wheat, which are other common food allergens. Hope this will be helpful to you. I would like to know the final diagnosis. Please do not hesitate to contact. Regards.