Vaginal Yeast Infection: This is often the most common cause of sudden vaginal burning, especially if accompanied by itching, redness, and a thick, white discharge. The sudden onset can be triggered by various factors including antibiotic use, hormonal changes, or poor hygiene.

Bacterial Vaginosis (BV): Characterized by an imbalance in the natural vaginal flora, leading to symptoms like burning, itching, and an abnormal discharge with a fishy odor. The onset can be sudden and is often associated with sexual activity or douching.
Urinary Tract Infection (UTI): While primarily affecting the urinary system, UTIs can cause vaginal burning, especially during urination. The sudden onset of dysuria (painful urination), frequent urination, and abdominal discomfort are key indicators.
Vaginal Atrophy: Common in postmenopausal women, vaginal atrophy can lead to vaginal dryness, burning, and pain during intercourse due to the decrease in estrogen levels.

Herpes Simplex Virus (HSV): Although less common, genital herpes can cause sudden, severe vaginal burning, especially during an initial outbreak. It's crucial to consider this diagnosis due to its implications for sexual health and the need for antiviral treatment.
Gonorrhea or Chlamydia: These sexually transmitted infections (STIs) can cause vaginal burning, among other symptoms like abnormal discharge and pelvic pain. Early diagnosis and treatment are essential to prevent long-term complications.
Vulvar or Vaginal Cancer: Though rare, any persistent or severe vaginal burning, especially in older women or those with risk factors, warrants further investigation to rule out malignancy.

Lichen Sclerosus: A rare condition that creates patchy, white skin in the genital area, which can lead to burning, itching, and pain. It's more common in postmenopausal women but can occur at any age.
Desquamative Inflammatory Vaginitis (DIV): Characterized by a sudden onset of vaginal burning, itching, and a purulent discharge. It's a rare condition with an unclear cause, requiring specific diagnostic tests for identification.
Vulvodynia: A chronic condition involving persistent, unexplained pain in the vulva, which can include burning sensations. The diagnosis is often one of exclusion, after ruling out other causes of vulvar pain.