What makes hives come out, and do the different types of allergies cause different sizes or different types of hives?

Not related to type: Hives are the result of an allergic reaction which causes a chemical called histamine to be released into the skin. It is irritating, which causes itching; it increases blood flow and leakage of tiny blood vessels, causing redness, swelling, and welts. There isn't a relation between type of allergen and the intensity of the hives; it's more the intensity of the reaction of the individual person.

Various: Hives can be caused by exposure to allergens in the environment, or various internal problems such as autoimmune to thyroid problems. Unfortunately, the size, location, and distribution of hives do not offer any clues as to why they're there.