There are several substitutes available - including formulas containing cows’ milk proteins which have been changed or broken down (these are called ‘hydrolysed formulas’)and formulas that contain no cows’ milk protein at all (these are sometimes called ‘amino acid-based formulas’).
Because all children need proteins for growth and development, proteins can’t be completely removed from your child’s diet. So milk proteins must be replaced by alternatives. However, the majority of infant milk formulas you may be familiar with contain ‘intact or whole’ milk proteins and protein fragments (in other words, cows’ milk proteins which haven’t been changed or broken down). So many baby milk formulas aren’t suitable either.