Angioedema: This condition is characterized by the rapid swelling of the dermis, subcutaneous tissue, mucosa, and submucosal tissues. It can be caused by allergic reactions, often to foods, medications, or insect bites, and can also be hereditary. The swelling typically involves the face, lips, tongue, and upper limbs, making it the most likely diagnosis for acute swelling in these areas.

Urticaria (Hives): While urticaria typically presents with wheals that are itchy and can appear anywhere on the body, in some cases, it can cause significant swelling, especially if it's part of an allergic reaction. The swelling might not be as deep as in angioedema but can still cause significant discomfort and cosmetic concern.
Allergic Contact Dermatitis: This is a type IV hypersensitivity reaction that occurs after exposure to an allergen. It can cause swelling, especially if the allergen was in contact with a large area of skin on the face or upper limbs. However, the reaction usually takes longer to develop than angioedema or urticaria.
Insect Bite or Sting Allergy: Reactions to insect bites or stings can range from mild to severe. In some cases, they can cause significant swelling in the affected area, which could involve the face or upper limbs if that's where the bite or sting occurred.

Anaphylaxis: Although anaphylaxis is a systemic, life-threatening allergic reaction that can cause a wide range of symptoms, including respiratory distress, cardiovascular collapse, and gastrointestinal symptoms, it can initially present with swelling of the face and upper limbs. It's crucial to recognize anaphylaxis early because it requires immediate treatment.
Hereditary Angioedema: This is a rare but potentially life-threatening condition caused by a deficiency or dysfunction of C1 esterase inhibitor. It can cause recurrent episodes of angioedema without the typical allergic symptoms, and the swelling can sometimes affect the airways, leading to asphyxiation.

Erythema Multiforme: A skin condition characterized by target lesions, which can sometimes be accompanied by swelling, especially if there's significant mucosal involvement. It's usually triggered by infections or medications.
Superior Vena Cava Syndrome: Obstruction of the superior vena cava can cause facial and upper limb swelling due to impaired venous return. This condition is more commonly associated with malignancies or thrombosis rather than allergic reactions.
Scleroderma: A chronic autoimmune disease that can cause skin thickening and swelling, among other symptoms. The swelling in scleroderma is typically more gradual and accompanied by other systemic symptoms.