I have spotted the signs with my son, first at 4mths he had an allergy,thought to be to gluton and milk, after many doctors and hosp visits it disappeared.
At 1yr he became lactose intolerant, though that went by the age of 2yrs.
Now almost 3years later he is again Lactose Intolerant, though this time I don't think it will go, it seems alot worse this time