Child Losing Weight, Dark Stools, Sweet Smell
Thanks for posting your query.
Considering the information you have provided your child could most probably have a gastroenteritis or a bowel disorder like lactose intolerance / milk allergy which has caused the change in his stools ( sweet smelling XXXXXXX undigested stools) .
As he has lost weight it's definitely worth taking him to his pediatrician for confirming the cause of the weight loss and gastroenteritis .
Your doctor would most probably order a stool routine and culture test for confirming the diagnosis and start appropriate treatment as per the cause .
Meanwhile you may try giving him a lactose free diet ( soy milk / cereal mix like nusobee etc) . Also make sure he is well hydrated though he is not having watery stools he might require more than usual amount of water intake .If you have recently made any changes in his diet kindly notify your doctor .
Multivitamin and zinc supplements and probiotics as per your doctors prescription might help in decreasing his symptoms .
Please do not worry as majority of such diarrhoea or malabsorption in toddlers are self limiting and not XXXXXXX .
Hope I have answered your query.
Wishing your child a speedy recovery.
Regards