Cellulitis: This is the most common cause of external ear swelling and pain, often resulting from bacterial infection, typically Staphylococcus aureus or Streptococcus pyogenes. The infection can spread from a local source, such as an infected piercing or a scratch.

Otitis Externa (Swimmer's Ear): An infection of the outer ear canal, often caused by bacterial (Pseudomonas aeruginosa) or fungal pathogens. It's common in individuals who swim frequently or have excessive moisture in the ear canal.
Furuncle or Carbuncle: A localized infection of the hair follicle or sebaceous gland in the external ear, usually caused by Staphylococcus aureus. It presents as a painful, swollen nodule.
Allergic Contact Dermatitis: An allergic reaction to substances like nickel in earrings, certain soaps, or hair products, leading to itching, redness, and swelling of the external ear.

Necrotizing Otitis Externa: A severe, potentially life-threatening infection that spreads to the cartilage and bone of the external ear, often seen in diabetic or immunocompromised patients. It requires prompt recognition and treatment.
Malignant Otitis Externa: Similar to necrotizing otitis externa but with a more aggressive course, often involving the temporal bone and requiring immediate medical attention.
Relapsing Polychondritis: An autoimmune disorder that can cause cartilage inflammation, leading to swelling and pain of the external ear, among other symptoms. It's crucial to diagnose due to its potential to affect other cartilaginous structures.

Gout: Although rare, gout can cause swelling and pain in the external ear, particularly if there are urate deposits in the helix or antihelix.
Sarcoidosis: A systemic disease that can cause granulomatous inflammation in various parts of the body, including the external ear, leading to swelling and pain.
Erythema Multiforme: An immune-mediated condition that can cause target lesions and swelling, including in the external ear, often in response to infections or medications.