Acute or Chronic Urticaria: This is the most common cause of hives, which can be triggered by various factors such as allergies, infections, or autoimmune reactions. The intermittent nature of the hives ("off and on") fits with the typical presentation of urticaria.

Allergic Reactions: Allergies to foods, drugs, or environmental factors can cause recurrent hives. Identifying and avoiding the allergen can help manage the condition.
Insect Bites or Stings: Repeated exposure to insect bites or stings can lead to intermittent hives.
Autoimmune Disorders: Conditions like thyroiditis or lupus can cause urticaria due to the body's immune response.

Anaphylaxis: Although rare, anaphylaxis is a life-threatening condition that can present with hives, among other symptoms like difficulty breathing and rapid heartbeat. It requires immediate medical attention.
Mastocytosis: A condition characterized by the accumulation of mast cells in the skin, which can cause hives, flushing, and other symptoms. It can be associated with systemic symptoms and requires prompt diagnosis.
Vasculitis: Inflammation of the blood vessels can cause hives, but it may also lead to more severe complications like organ damage if not treated.

Hereditary Angioedema: A genetic disorder that causes recurrent episodes of severe swelling, including hives, due to deficiency or dysfunction of C1 esterase inhibitor.
Solar Urticaria: A rare condition where hives are triggered by exposure to sunlight.
Cold Urticaria: Hives that occur in response to cold temperatures, which can be a standalone condition or part of a broader syndrome.
Cholinergic Urticaria: Hives triggered by a rise in body temperature, often due to exercise, hot showers, or emotional stress.