It depends. You should inform your doctor if you keep getting hives that last a month or more. You should get medical help immediately if any of these things occur:
You start to get burning or itchy welts in your throat. You get hives and a dry cough, cold, sweat, nausea, dizziness, or trouble breathing after an insect bite, sting, or new medication. This may be anaphylaxis – an extreme allergic reaction. You have symptoms of angioedema (this is swelling of the lips, tongue, or throat). You need immediate medical attention so that the swelling doesn’t block the air passage to the lungs.