My wife shows every symptom for chronic urticaria but the auto-immune test came back negative. Is it possible it's a false negative?

Hives. Hives becomes chronic when it lasts for greater than 6 weeks. The most common cause is idiopathic- cause unknown. If the hives lasts less than 24 hrs in one given spot it is unlikely to have an autoimmune cause. See an allergist to help find the best combination of medications to control the hives.