Acute Urticaria: This is the most common cause of whole body hives, often triggered by allergic reactions to foods, medications, or infections. It presents with sudden onset of itchy, raised wheals that can appear anywhere on the body.

Chronic Urticaria: Similar to acute urticaria but lasts more than 6 weeks. Causes can be autoimmune, allergic, or idiopathic.
Insect Sting or Bite Allergy: Allergic reactions to insect stings or bites can cause whole body hives, especially in individuals with a known history of such allergies.
Drug Allergy: Many medications can cause urticaria as an allergic reaction, including antibiotics, NSAIDs, and blood pressure medications.

Anaphylaxis: A severe, life-threatening allergic reaction that can present with whole body hives, along with other symptoms like difficulty breathing, rapid heartbeat, and a drop in blood pressure. Immediate medical attention is required.
Mastocytosis: A condition characterized by the accumulation of mast cells in the skin and other organs, which can cause urticaria, among other symptoms.
Autoimmune Disorders: Certain autoimmune conditions, such as lupus or rheumatoid arthritis, can occasionally present with urticaria.

Urticarial Vasculitis: An inflammation of the blood vessels that can cause urticaria-like lesions, but these are typically more painful and can leave bruises.
Erythema Multiforme: A skin condition characterized by target-like lesions, which can sometimes resemble urticaria but is usually distinguished by its distinctive appearance and often associated with infections or medications.
Parasitic Infections: Certain parasitic infections, such as those caused by hookworms or roundworms, can very rarely cause urticaria as part of their symptomatology.