Cellulitis: This is the most likely diagnosis due to the presentation of redness and swelling over the conchal bowl and posterior ear area, which are common signs of a bacterial infection of the skin and subcutaneous tissue.

Contact Dermatitis: An allergic or irritant reaction to earrings, hair products, or other substances could cause redness and swelling in the affected area.
Furuncle or Carbuncle: A localized infection of the hair follicle or sebaceous gland could present with redness, swelling, and possibly pus.
Perichondritis: Inflammation of the tissue surrounding the cartilage of the ear, often caused by infection, could lead to redness and swelling, particularly if the conchal bowl is involved.

Necrotizing Otitis Externa: Although less common, this severe infection of the external auditory canal and surrounding tissues can present with similar symptoms and is more likely in diabetic or immunocompromised patients. It requires prompt recognition and treatment to prevent serious complications.
Relapsing Polychondritis: An autoimmune disorder that can cause cartilage inflammation, leading to ear redness and swelling, among other symptoms. Early diagnosis is crucial for managing the condition and preventing further cartilage damage.

Erythema Multiforme: A skin condition characterized by target lesions, which could potentially involve the ear and present with redness and swelling, though it's less common in this specific location.
Granuloma Faciale: A rare skin condition that could cause redness and swelling on the face, including the ears, though it's more typically seen on the forehead or cheeks.