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InfectiousICD-10: B00.1Approximately 67% of the global population under age 50 is infected with HSV-1

Cold Sores (Oral Herpes)

Also known as: Oral Herpes, Fever Blisters, HSV-1, Herpes Labialis

Cold sores are small, fluid-filled blisters that typically appear on or around the lips, caused by the herpes simplex virus type 1 (HSV-1). After the initial infection, the virus remains dormant in nerve cells and can reactivate periodically, causing recurrent outbreaks often triggered by stress, illness, or sun exposure. Cold sores are highly contagious, especially when blisters are open and oozing, and affect a significant portion of the global population.

Symptoms

Tingling, itching, or burning sensation around the lips before blisters appear
Small, fluid-filled blisters on or around the lips
Blisters that break open, ooze, and form a crust
Pain and tenderness around the affected area
Swelling and redness around the blisters
Fever, sore throat, and swollen lymph nodes during the first outbreak
Headache and muscle aches during initial infection

Causes

  • Herpes simplex virus type 1 (HSV-1) infection
  • Reactivation of dormant virus in the trigeminal ganglion nerve
  • Less commonly, herpes simplex virus type 2 (HSV-2) through oral-genital contact
  • Transmission through direct contact with an active lesion or infected saliva

Risk Factors

  • Close personal contact with someone who has an active cold sore
  • Weakened immune system from illness or immunosuppressive therapy
  • Excessive sun exposure without lip protection
  • Physical or emotional stress
  • Hormonal changes such as menstruation
  • Dental procedures or facial trauma

Diagnosis

  • Visual examination of the characteristic blisters
  • Viral culture from a fluid sample of an active blister
  • PCR (polymerase chain reaction) testing for HSV DNA
  • Blood test for HSV antibodies to confirm past infection

Treatment

  • Oral antiviral medications (valacyclovir, acyclovir, famciclovir) to shorten outbreaks
  • Topical antiviral creams (penciclovir, acyclovir cream) for early treatment
  • Over-the-counter pain relievers (ibuprofen, acetaminophen) for discomfort
  • Docosanol (Abreva) topical cream for over-the-counter management
  • Suppressive antiviral therapy for frequent outbreaks (6+ per year)

Prevention

  • Avoid kissing or sharing utensils when cold sores are present
  • Apply sunscreen or lip balm with SPF to prevent sun-triggered outbreaks
  • Manage stress through relaxation techniques and adequate sleep
  • Wash hands frequently, especially after touching a cold sore
  • Avoid touching cold sores to prevent spreading to other body parts

When to See a Doctor

  • Cold sores do not heal within 2 weeks
  • You experience frequent outbreaks (6 or more per year)
  • You have a weakened immune system and develop cold sores
  • Cold sores spread to the eyes, causing pain or blurred vision

Frequently Asked Questions

Related Conditions

Eczema

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Psoriasis

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Acne Vulgaris

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