If you have a milk allergy, using A2 milk won't make any difference, as its still a caesin protein.
The main difference between A1 and A2 milk is that when its digested, the caesin protein chain breaks at a different point and forms different compounds during digestion.
Most of the cows used in our dairy farming are A1 cows. I can't remember the exact percentages, but about 10% of our normal dairy cows are A2. In herds of A2 cows, they genetically test the cows to make sure they are certified A2.
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