Cold sores, or fever blisters, are caused mainly by the herpes simplex virus type 1 (HSV-1), and sometimes HSV-2. They spread easily through direct contact like kissing or sharing items, and even through self-infection by touching a sore then another body part.Symptoms start with tingling or itching, followed by fluid-filled blisters, painful open sores, and finally scabbing. “A typical outbreak lasts about 7 to 10 days.” Triggers include stress, illness, sun exposure, hormonal changes, and a weakened immune system.

There’s no cure, but antiviral pills (e.g. acyclovir), topical creams, pain relievers, and moisturizers help manage symptoms. Prevent outbreaks by avoiding contact during flare-ups and supporting your immune system.Unexpectedly, cold sores may be linked to Alzheimer’s. A 2019 study found gum disease bacteria *P. gingivalis* and its toxic enzymes, gingipains, in the brains of deceased people—some not even diagnosed with dementia. “Our identification of gingipain antigens… argues that brain infection… is an early event,” researchers wrote.

Though treatments like COR388 showed promise in mice, experts urge caution: “It’s important that we test as many approaches as possible,” said Alzheimer’s Research UK’s David Reynolds.