Cold sores, or fever blisters, are a common infection caused mainly by herpes simplex virus type 1 (HSV-1), though HSV-2 can also cause them. They spread easily through direct contact, such as kissing, or indirectly via shared items like towels or lip balm. Touching a sore and then another body part can also spread the virus.

An outbreak often starts with “tingling or itching a day or two before appearance,” followed by blisters near the lips, rupture into painful sores, and scabbing. Healing usually takes 7–10 days, but the virus stays dormant and can reactivate. Triggers include stress, sun, illness, hormonal changes, and weak immunity. There’s no cure, but antiviral pills such as acyclovir or valacyclovir can shorten outbreaks, while creams, pain relievers, and moisturizers ease symptoms.

Prevention includes avoiding close contact during outbreaks, not sharing personal items, using lip sunscreen, and maintaining overall health. Seek medical help for frequent, severe, or spreading sores, especially with a weakened immune system.

Interestingly, research links gum disease bacteria *P. gingivalis* to Alzheimer’s disease. Toxic enzymes called gingipains were found in brains even before dementia symptoms. In mice, the compound COR388 reduced brain damage, suggesting early infection may play a role.