It usually starts around 2 weeks and continues until about 3 months, but it can start any time and continue much longer. My daughter started with colic 10 days old and didn't really stop until 4 months, and even after that she was a hard baby.
A LOT of the time colic is due to dairy sensitivity. If you are breastfeeding try eliminating dairy from your diet for a while. If you are formula feeding, try a dairy-free formula and see if it helps. Dairy proteins are much larger than little babies are made to handle and so it can cause problems for them. My son started to get colicky at 2 weeks old, I eliminated dairy and he was a happy baby. He was 6 months old before I could eat much dairy again, but it was worth it.
at 1:46 AM on Jun. 28, 2011