Irritant Contact Dermatitis: This is the most likely diagnosis due to the high prevalence of exposure to irritants such as soaps, douches, or spermicides that can cause vaginal irritation without an infectious etiology.

Allergic Contact Dermatitis: Similar to irritant contact dermatitis but involves an allergic reaction, often to products like latex condoms, lubricants, or certain fabrics.
Atrophic Vaginitis: Common in postmenopausal women due to decreased estrogen levels, leading to thinning and drying of the vaginal walls, which can cause irritation.
Vulvar Lichen Sclerosus: A chronic inflammatory skin condition that can cause itching, burning, and pain in the vulvar area.

Lichen Planus: Although less common, it can cause significant morbidity if not treated. It presents with erosive lesions and can lead to scarring.
Vulvar Intraepithelial Neoplasia (VIN): A precancerous condition that can cause irritation and requires early detection to prevent progression to invasive cancer.
Paget's Disease of the Vulva: A rare form of vulvar cancer that can present with itching and irritation, making early diagnosis critical.

Desquamative Inflammatory Vaginitis (DIV): A rare condition characterized by a purulent vaginal discharge and significant inflammation, often misdiagnosed as an infection.
Vulvar Crohn's Disease: A manifestation of Crohn's disease that can affect the vulva, causing irritation, ulcers, and fistulas.
Sjögren's Syndrome: An autoimmune disorder that can lead to vaginal dryness and irritation due to decreased mucous membrane secretions.