The first day of symptoms include fever and runny nose. It is often not until about the second or third day that the rash develops. First, you need to make sure that your baby is truly constipated. Many newborns grunt and squirm and get quite red in the face when passing normal stools. This is not constipation.
True constipation is very infrequent stools, which are firm or formed in consistency.
Remember that some normal breast fed newborns may stool as seldom as once a week. This can be very normal. Then talk to your doctor about adding small amounts of water. Then, if necessary, add diluted fruit juice to your baby's diet. You may also need to discuss with your pediatrician the use of fruits, medicines, or dark corn syrup depending upon your baby's age and your physician's preferences.