Trauma or Injury: This is often the most common cause of whole hand swelling, resulting from accidents, sports injuries, or other forms of physical trauma. The swelling can be due to bruising, hematoma, or soft tissue injury.

Infection (Cellulitis or Abscess): Bacterial infections can cause significant swelling of the hand, often accompanied by redness, warmth, and pain. These infections can arise from minor cuts or puncture wounds.
Allergic Reaction: An allergic reaction to an insect bite, sting, or contact with an allergen can cause swelling of the hand, which may be accompanied by itching, redness, and blistering.
Rheumatologic Conditions: Conditions like rheumatoid arthritis can cause swelling in the hands due to inflammation of the joints.

Compartment Syndrome: A serious condition that occurs when pressure within the muscles builds to dangerous levels, cutting off blood flow and preventing nourishment and oxygen from reaching nerve and muscle cells. It requires immediate medical attention.
Necrotizing Fasciitis: A severe infection that destroys the tissue under the skin, including fat and the tissue covering the muscles (fascia). It's a medical emergency.
Deep Vein Thrombosis (DVT): Although more common in the legs, DVT can occur in the arms and hands, especially after trauma or prolonged immobilization. It poses a risk of pulmonary embolism.

Sarcoidosis: A disease characterized by the growth of tiny collections of inflammatory cells (granulomas) in any part of the body — most commonly the lungs and lymph nodes — but can also affect the skin and joints, leading to swelling.
Angioedema: A rare condition characterized by the rapid swelling of the dermis, subcutaneous tissue, mucosa, and submucosal tissues. It can be hereditary or acquired.
Complex Regional Pain Syndrome (CRPS): A chronic pain condition characterized by severe, burning pain at the site of an injury, which can also cause swelling and changes in skin temperature and color.