From what I know -- you need to be "allergen free" for 2 weeks before reintroducing your milk. Even then, it could be something different other then dairy (dairy is always the main go to). We thought J.J had a dairy issue too but it turned out to be eggs. If you want to figure out what he is really allergic to, you need to exclude all the main allergens from your diet -- Wheat, Diary, Eggs, Peanuts, Tree Nuts, Soy, etc. Then introduce one back into your diet at a time and see how he is. Once you introduce something and he gets a rash, you found your allergen. Most allergists won't test him until he is 1.
What symptoms did your child have? Rash all over his stomach (little red bumps) that would itch him like crazy. A more severe allergic reaction caused the bumps on his stomach legs and arms. Benedryl is the cure, but the rash still lingers for 2-3 days.
How were they diagnosed? We did skin allergy testing as soon as he turned 1, that was confirmed by blood testing. J.J has a moderate-severe egg allergy and other unknown allergies.
Did you do an exclusion diet? Once we found out about the egg, we removed egg from his diet.
How long did it take for you to see an improvement in your child? As soon as we removed his allergy he was fine. Sometimes he gets a reaction and we don't know from what. We suspect he has an allergy to cottonseed oil (very rare allergy).
Did they outgrow the allergy at all? Nope. We were told if he still is this way by 5, he likely will be for life. He shows no signs of getting rid of the allergy.
We knew he had a problem with my milk because he was SO unhappy. We had no choice but to switch him to formula because there are very few foods I eat as is so an exclusion diet for me was out of the questions. Once he was on formula he improved, but it's been a battle his whole life with milk. My milk caused tons of trouble. Regular formula also caused him gastric issues and issues with congestion (which can be a sign of an allergy). Soy formula made things 75% better but not all the way (still congested). He can't have whole milk, his stomach gets VERY upset and he gets congested. Lactaid milk bothers him too (stomach problems). Rice milk he likes but we think he might have a problem with that too (or certain brands). We are about to try soy milk next as a last resort before trying almond milk.
I hope that helps