Cold sores, or fever blisters, are small fluid-filled lesions caused by the herpes simplex virus type 1 (HSV-1). Around 67% of people under 50 carry HSV-1, often without symptoms. When active, it causes recurring sores, usually on or around the lips. The virus spreads through oral contact and remains dormant in nerve cells, reactivating due to triggers like stress, illness, sun exposure, or hormonal...