My son has contact dermatitis on his belly and on eggs from cow's milk…

My son has contact dermatitis on his belly and on eggs from cow's milk, he went to an allergist who prescribed a ton of tests for 30K and medications. I read somewhere that allergies themselves will pass through in some time, so I'm thinking about just waiting and not giving any allergens or all the same buying medication and doing tests. Even if I do the tests what good will they be? Anyway, I know there is allergy, so it's allergy. I also read that some vaccines have chicken embryo, like a vaccine against cholera, decided that I won't vaccinate my son until he's one year old. He was also prescribed a strict diet, except for vegetables, nothing else can be eaten