Please suggest which formula milk is best for my 4 months old baby.

I would like to recommend plant based milk such as soy milk, almond milk which are more digestable by babies. Formula milk contains animal protein which is normally the main allergen source such as eczema, tummy discomfort and etc. You may refer to this website for a comparison between plant based milk and animal based milk. http://plantbasedresearch.org/content/animal-milk-vs-plant-milk However, when you purchase plant based milk, do look for organic and Non-GMO by reading the labels on the product. When your baby is ready for weaning, try to incorporate as much as fruits and vegetables into her/his diet to build up the immunnity instead of depending on milk to get the nutrients.