Most of the time urticaria (hives) and angioedema (deep swellings under the skin) are manifestations of an allergic reaction triggered by medications, foods, infections, certain physical agents like heat, cold, water, sun, other allergens and systemic illnesses.
Next Steps
The diagnostic work-up includes blood tests, urine, stool to check for parasites, and x-rays of the chest, sinuses and teeth. A prick or scratch test to test for airborn or food allergens is also in order.