What Causes Hives That Come and Go for Weeks?

Chronic urticaria, or hives lasting over six weeks, typically results from autoimmune reactions rather than allergies. In 80-90% of chronic cases, the immune system mistakenly attacks healthy skin cells, releasing histamine and causing recurring welts. Common triggers include stress, hormones, certain medications, infections, or underlying autoimmune conditions like thyroid disease. Unlike acute hives from food allergies, chronic hives rarely have identifiable external triggers. Heat, cold, pressure, or exercise can worsen symptoms. Most chronic urticaria cases resolve within 1-5 years, though some persist longer. Antihistamines provide relief, while severe cases may require immunosuppressive treatments or omalizumab injections.