What Coming Out of Your Mouth Could Mean You’re Infected

Cold Sores and a Surprising Link to Alzheimer’s Disease

Cold sores—commonly called fever blisters—are a widespread viral infection most often caused by the herpes simplex virus type 1 (HSV-1). In some cases, herpes simplex virus type 2 (HSV-2), which is usually linked to genital herpes, can also cause cold sores through oral-genital contact.

How Cold Sores Spread

Cold sores are highly contagious and can be transmitted through:

Direct contact – kissing or sharing food, drinks, or utensils with an infected person

Indirect contact – touching contaminated items like towels, lip balm, or cutlery

Self-infection – touching a sore and then your eyes, genitals, or other areas of skin

Recognizing the Symptoms

Cold sores usually progress through these stages:

Tingling or itching – a burning or itchy feeling appears 1–2 days before a sore develops

Blister formation – small fluid-filled blisters emerge, usually on the lips, but sometimes on the nose or gums

Blister rupture – blisters break, leaving painful open sores (the most contagious stage)

Scabbing – sores dry, form a crust, and heal within 7–10 days

Even after healing, the virus stays dormant in the body and can reactivate later.

Common Outbreak Triggers

Factors that may cause the virus to resurface include:

• Stress (emotional or physical)
  
  
• Sun exposure or UV light
  
  
• Hormonal changes (menstruation, pregnancy)
  
  
• Illnesses such as colds or fevers
  
  
• Weakened immune system

Managing Cold Sores

There’s no cure, but treatment can reduce symptoms and speed recovery:

Antiviral tablets – acyclovir, valacyclovir, or famciclovir work best if taken early

Topical antiviral creams – may relieve symptoms and limit spread

Pain relief – ibuprofen, acetaminophen, or numbing ointments

Moisturizing lip balms – reduce dryness and discomfort

Preventing Cold Sores

• Avoid kissing or close contact during an outbreak
  
  
• Don’t share personal items like lip balm or utensils
  
  
• Use lip sunscreen if sunlight is a trigger
  
  
• Support your immune system with a healthy lifestyle

When to See a Doctor

Seek medical advice if:

• Outbreaks are frequent or severe
  
  
• Over-the-counter treatments don’t help
  
  
• Sores spread beyond the lips
  
  
• Pain makes eating, drinking, or talking difficult
  
  
• You have a weakened immune system

The Possible Alzheimer’s Connection

While cold sores themselves are well understood, new research hints at a surprising link between oral infections and Alzheimer’s disease—the most common cause of dementia in the UK.

Some studies suggest that Alzheimer’s might, in part, be triggered by infection. In 2019, scientists found a potential connection between Alzheimer’s and gum disease caused by the bacterium Porphyromonas gingivalis.

Researchers detected high levels of P. gingivalis’ toxic enzymes (gingipains) in the brains of Alzheimer’s patients, as well as in people who had Alzheimer’s-related brain changes but were never diagnosed with dementia. This suggests the infection might occur early—before memory loss begins—rather than as a side effect of the disease.

In mouse studies, a drug developed to block gingipains (COR388) reduced both amyloid-beta buildup and brain inflammation.

While these treatments are far from being proven in humans, experts like David Reynolds of Alzheimer’s Research UK emphasize that, with no major dementia breakthroughs in over 15 years, exploring such links is vital.