Food allergies, medication allergies or environmental allergens can cause hives and swelling, but these reactions generally appear within 90 minutes after the exposure. If the reaction is immediate, it is easier to make the connection. If a food is the cause, the hives or angioedema will reoccur whenever that food is ingested. Hives or angioedema with swelling of the throat can be life threatening and may require epinephrine.
More About Urticaria Angiodema: