Allergic reaction: This is often the most common cause of facial swelling, typically presenting with sudden onset, itching, and possibly accompanied by other symptoms like hives or difficulty breathing. The reaction could be due to various allergens such as foods, insect bites, or medications.

Dental infection or abscess: Infections originating from dental issues can cause significant facial swelling, especially if the infection spreads to the surrounding tissues. Symptoms may include toothache, fever, and localized pain.
Sinusitis: Inflammation or infection of the sinuses can lead to facial swelling, particularly in the areas surrounding the sinuses. Other symptoms might include nasal congestion, headache, and facial pain.
Trauma: Physical injury to the face can result in swelling due to bruising or hematoma formation. The history of trauma and the presence of other signs of injury can help in diagnosing this condition.

Angioedema: A potentially life-threatening condition characterized by rapid swelling of the dermis, subcutaneous tissue, mucosa, and submucosal tissues. It can be hereditary or acquired and may compromise the airway if not promptly treated.
Cellulitis: A bacterial infection of the skin and subcutaneous tissues that can cause facial swelling, redness, and warmth. It requires prompt antibiotic treatment to prevent complications.
Orbital cellulitis: An infection of the tissues surrounding the eye, which can cause swelling of the face, particularly around the eye, and may lead to serious complications if not treated aggressively.

Sjögren's syndrome: An autoimmune disorder that can cause swelling of the salivary and lacrimal glands, leading to facial swelling among other symptoms like dry mouth and eyes.
Granulomatosis with polyangiitis (formerly known as Wegener's granulomatosis): A rare autoimmune disorder that can cause inflammation of the blood vessels, leading to a variety of symptoms including facial swelling, sinusitis, and kidney problems.
Melkersson-Rosenthal syndrome: A rare neurological disorder characterized by recurrent, often unilateral, facial paralysis or weakness, facial edema, and the development of folds and furrows in the tongue (fissured tongue).