Did you try soy by chance? LO didn't do well on Alimentum, but is doing great on soy. My pedi was against trying it because of the high correlation between dairy and soy allergies, but he's been great so she ate her words.
We started to see a difference on Alimentum within 24 hours. I would say it took about a week to really see a major difference though, so don't give up hope if you aren't seeing a change right away.
We saw some changes within a day or two, but it took almost a full 2 weeks to completely take effect. She just continued to have excessive bowel movements and sever blistering diaper rash. But now nine weeks later she is a happy comfy baby
Re: If you're feeding your LO Alimentium