Well if at all your kid is having outside food( junk, bakery, chips, pastries) STOP it. Try to include home based diet which includes ample amount of fruits and vegetables Plenty of fruit juices made at home can be given Tender coconut water can be given Include curd and buttermilk in his diet. Make sure his hands are clean, nails are cut if he is using his hands to eat. These small changes would make a difference and slowly you will see changes.