Mystery case answer

This is Arwen, a 3,5 years old, spayed Viszla. Her skin lesions started soon after developing diarrhea and vomiting. She was treated with immuno-suppressive doses of glucocorticoids and recovered very slowly.
Main important question was: asking for medications, food history and possible insect bites
We found out that Arwen was eating often walnuts and that day more then 100g.
What is your problem list? Urticaria and erythematous patches, vomiting and diarrhea
What are your main differentials?  Urticaria, urticarial vasculitis
What tests would you like to perform? Checking clinical signs of anaphylaxis (inlcuding blood preassure), hematology, biochemistry, abdominal ultrasound, skin biopsy, intradermal testing and western blot for walnuts 
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