What if my baby has brown spots on his body?

Brown spots?: There are many causes of hyperpigmentation. For example, Mongolian spots are common and nothing to worry about. Cafe au lait spots may need to be followed. Ask you pediatrician - since they can actually see the "brown spots" you are referring to they are in the best position to give them a name and let you know the significance. Internet "guessing" is likely only going to cause undue anxiety.