I would see a new allergist as already stated, and make sure to see a pediatric allergist. We had a negative experience with the first allergist we saw.
DD has a milk protein allergy. Blood and skin tests come back negative. She has a non-IgE mediated allergy, there is no reliable way to test for it. DS, her twin brother has a non-IgE mediated allergy to soy protein, although his reaction is typically less severe. When DD has milk protein, she experience delayed violent vomiting, goes limp and appears extremely weak. She vomits until she has nothing left in her system and typically can't hold anything down for a day or so after. DS has delayed vomiting from soy, but it's not as severe. We test to see if they have grown out of their allergies by hospital food challenges (so they are closely monitored and hooked up to IV).
We think DS may also have a peanut allergy because he got a hive and vomited when he tried a miniscule amount of peanut butter. But, his skin test did not show it. He got two satellite hives, not at the site of the peanut test, elsewhere on his body when we did skin testing. So, we just avoid peanut butter for now and carry an Epi Pen.