Milk allergy

Does anyone have any experience with milk allergies in young infants? I looked online for symptoms, but wanted some first had experience stories. I am wondering if I need to switch my daughter back to soy and just deal with her constipation from it. Her pediatrician told us she would support whatever we decide works best for her. We have her on gentlease right now. I'm not sure if some of her symptoms are from teething and being introduced to solids.

Thanks in advance for any advice/stories anyone has to share.