While there are many brands of "hypoallergenic" formula milk in the market, there are only a handful of milk formula with proteins that contain proteins that are completely hydrolyzed or cut up into its amino acid components and therefore do not elicit allergic reactions. One of these is Nutramigen AA, manufactured by Mead Johnson. This is what my son switched to after he was diagnosed of having cow milk allergies. The so-called HA or hypoallergenic formula were not suitable to manage his allergies.

Some product details from the website:

-Amino acid-based, hypoallergenic formula
-Scientifically designed for infants and toddlers with severe cow's milk protein allergies and/or multiple food protein allergies
-Nutritionally complete*
-Iron fortified
-Includes LIPIL, our blend of DHA and ARA, nutrients also found in breast milk that promote brain and eye development
-Can be your baby's only food for up to age 6 months, and a large part of your child's diet through 24 months of age

At around 18 months, we switched him to calcium-fortified rice milk. By that time, he was eating solids quite well and well, Nutramigen is not exactly cheap...