Wife has adhoc itchy allergy rashes appear all over body, face everywhere. can last days. been to specialist but no luck. how to get diagnosed?

? urticaria: if you mean no clear trigger (food/medicine), it can be idiopathic urticaria, acute type is usually due to a viral infection, while chronic type, (been there for 6 weeks or more) has no clear reason, but subtle problems need to be ruled out first as hormonal or autoimmune issues, C a dermatologist/allergist. OTC loratadine or cetirizine taken regularly can help, read the labels carefully, goodluck