Are hives caused by contact substances or internal substances such as food?

Yes: Acute urticaria can be caused by contact and/or injected allergens. Common examples include exotic woods and pets for contact, and peanut or drug for ingested.

Both: Release of histamine a causes hives in response to either contact or ingested substance.

Hives: Hives are caused by a severe allergic reaction which can be internally or externally initiated.

Can be either: Hives can be caused by food, contact with substances, stress, cold, exercise, etc. They are simply a reaction to something and not specific for any one cause. If there is any shortness of breath, tightness in the chest or chest pain seek immediate medical evaluation.