My first DD got so constipated when we swiched her to cow's milk at 12months. She had been on soy then Lacto-Free formula prior. She ended up in the ER b/c she had blood in her stool.
I swore that it was the milk allergy causing the issue but every doc thought I was crazy. She started seeing a pedi GI at 2 and has been on Miralax since then. She will be 6 in March.
About a year ago I took her to an allergy doc and told him about the constipation and he said that it is the #1 sign of a milk allergy! I knew all along that was it b/c constipation started right when we intro the milk. And as soon as I started eliminating the milk from her diet I had to use less and less Miralax. But she still has to be on the Miralax b/c she is such a picky eater and milk is in everything!
So when my middle dd, Payton, turned 1 we decided to wait till 18 months to intro milk. This helped but I still suspect that she has a slight milk allergy. Too much in one day and she is also plugged up but not as sensitive as Jackie. She is now also on Miralax also. And Abby def has a milk/soy protein intolerance and in on Neocate which is amino acid based formula. So trying to switch to milk should be fun.
One thing that the pedi GI told us about is pear juice. Pears are a natural laxative and have worked great in our house. Gerber pear juice is the only kind that I think is available. Both Jackie and Payton get a sippy full in the morning along with the Miralax.
Just wondering, what type of formula was your dd on?
Good Luck, I hope you find something that helps.