Food sources like: nuts, soy, dairy, fish, eggs, tomatoes, certain food additives. Stress – if you are continuously stressing about hives your body will release histamine and in return you may get more hives. Certain medications like NSAIDS ( aspirin and ibuprofen), ACE inhibitors can cause hives. Infections, recent surgeries can also cause urticaria Presence of any other autoimmune conditions like thyroid.