I would go with your gut if further testing doesn't show anything. It's not always accurate (the testing ), and you are the one that sees the reactions first hand, so yeah, would probably continue avoiding.
Benadryl will help for the hives, but won't help for the GI symptoms unfortunately. That just has to be worked out of their system.
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What DIDN'T Gwyneth react to!! Lol Seriously, when we did patch testing i think they did 33 samples, and about 29-30 she reacted to, and they were pretty right on. She could only tolerate a few things for a long time. Then her diet started broadening, and the samples with the biggest reactions, milk, tomato and corn, are still a little dicey. She can do trace everything, and cheese, pizza, and just recently it looks like popcorn is ok. Ice cream was a big fail a couple of months ago, so heat milk products are looking ok. Basically straight up cows milk, and tomato.....but tomato is Turing into just a contact reaction (I think), she had huge rash/hives a few weeks ago after smearing herself with marina sauce....but stools were ok. We've been dealing with this for so long (since she was 3 weeks old), that these last remaining mysteries are welcomed over the many many from before. I went with my gut on almost every one and was usually right.
Hang in there!!!