Food Allergies Treatment

I don’t know where you are writing from, or who produces Herbalife, but all food/dietary supplement products, produced or distributed in the United States, are required to list allergen information on the package. Dairy is considered a potential allergen, so if you read the box, it should be pretty clear.
I would say though that I would be FAR MORE concerned about what else you are exposing your child to by using a product called HERBALife. Even the most common dietary supplements like ginkgo or echinacea are having severe interactions with prescribed medications. It has become such a concern that most doctors are now being instructed to not only ask “What other medications are you taking?” but also “How often do you drink protein shakes or energy drinks?”
I would be ESPECIALLY concerned about what types of supplements have been added to these shakes, as they are designed for weight loss in adults. It’s likely not something you would ever want to give to a developing infant who needs to GAIN weight. This is exactly what you would be doing though, if you were to drink it while breastfeeding.
Take your cue from the new practices of doctors and treat the herbal supplements in these shakes just as you would any other drug. Do not not use them until you have cleared it with your doctor.