Cold Sore Symptoms and Diagnosis
Dental & Oral HealthCold Sores

Cold Sore Symptoms and Diagnosis

Cold Sore Symptoms and Diagnosis
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Updated on March 22, 2024
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A cold sore or fever blister is caused by the herpes simplex virus (HSV). About 50 to 80 percent of American adults carry HSV type 1 (HSV-1), which is why this virus is the most common cause of cold sores — although HSV type 2 is also a possible culprit.

Once a person is infected with a cold sore, the virus enters the body and travels to the nerves, where it lies dormant until awakened.

Those infected with HSV can develop multiple cold sores throughout their lives, yet some people exposed to the virus never get a cold sore.

Cold sores are sometimes mistaken for other lesions that form in or around the mouth, such as canker sores. Since cold sores are contagious, it’s important that you know how to distinguish these sores from other sores and take the appropriate steps to stop the spread of the virus.

‘Do I Have a Cold Sore?’ Telltale Signs and Symptoms

The symptoms of a cold sore vary depending on whether it’s your first outbreak or a recurrent outbreak.

A cold sore causes tiny clusters of fluid-filled blisters on or around the lip or mouth. Unlike canker sores, cold sores don’t usually develop inside the mouth. But a first-time infection with HSV can produce a condition called acute herpetic gingivostomatitis, which is a painful eruption that causes swollen red gums, a fever, enlarged lymph nodes, and numerous sores on the tongue, lips, and inner cheeks, says Allison Arthur, MD, a dermatologist at Sand Lake Dermatology Center in Orlando, Florida.

Many people who have cold sores were exposed to HSV-1 during childhood, most likely after being kissed by someone who had the virus. Cold sore symptoms tend to be worse during the primary or first outbreak, with some people experiencing milder symptoms with recurrent outbreaks.

Other symptoms may occur if you’re newly infected, too:

  • Sore throat
  • Body aches
  • Headache
  • Nausea
  • Pain with swallowing
Cold sores start with an itchy or tingling sensation in the spot of development. This can last for one or two days, with a cold sore developing shortly thereafter. Other symptoms include redness, pain, or swelling at the spot of the sore.

After a few days, cold sores rupture and ooze pus-like fluid. A scab forms over the sore in its final stages. Cold sores heal in about one to two weeks without treatment, but they can heal sooner with treatment.

While cold sores often occur on or around the lips, they can also develop around the nose, cheek, and genital area. This can happen if you touch a cold sore and then touch another part of your body without washing your hands or if you engage in oral sex with someone who has a cold sore.

The virus can also spread to your eyes and cause a serious eye infection. So it’s important that you don’t touch your eyes if you have a cold sore.

Signs that the virus might have spread to your eyes include sensitivity to light, pain, swelling, irritation, or eyes that feel runny or gritty.

How Cold Sores Are Diagnosed

See a doctor if you’re not sure whether a lesion is a cold sore. In most cases, your doctor can diagnose a cold sore by looking at the lesion. To confirm a diagnosis, however, your doctor may take a fluid sample from the blister and send it to a lab to check for HSV-1.

Keep in mind that you don’t have to see a doctor for a cold sore. These are common infections that will clear on their own. Nonetheless, many medications can relieve symptoms and speed the healing process. These include over-the-counter antiviral medications, as well as oral pain relief creams and ointments.

Cold sores typically heal in about 7 to 10 days, so see a doctor if your sore doesn’t improve after two weeks, advises Amesh Adalja, MD, a senior scholar at Johns Hopkins Center for Health Security who is based in Pittsburgh.

In this situation, you may need a prescription antiviral medication, especially if you have an autoimmune disease or a weak immune system. Both factors will make it harder for your body to fight the virus.

Also, see a doctor if you have recurrent cold sores. Your doctor may prescribe an antiviral medication for everyday use, which can reduce the frequency and duration of outbreaks. An antiviral can also prevent the virus from spreading to your spinal cord or brain.

An antiviral is sometimes prescribed to people who have eczema. “In people with an underlying widespread skin disease, such as eczema, a cold sore outbreak can spread like wildfire throughout the skin, causing a severe infection known as eczema herpeticum,” says Dr. Arthur.

You should also seek medical attention if a cold sore spreads to your eyes. This type of eye infection can lead to complications such as scarring, vision problems, or even blindness.

A Final Word on Cold Sores Symptoms and Their Diagnosis

There’s no cure for HSV-1, so cold sores may return after treatment. But recognizing the signs and symptoms of a cold sore and starting treatment early may shorten the duration of an outbreak. And for those who live with frequent outbreaks, a daily antiviral might reduce the frequency of cold sores.

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Natalia Johnsen, MD

Medical Reviewer
Member of American College of Lifestyle Medicine

Natalia Johnsen, MD, is a triple board-certified physician in internal medicine, lifestyle medicine, and obesity medicine, practicing as an internist and consultant at the Vancouver Clinic in Vancouver, Washington.

Dr. Johnsen began her medical career as an ob-gyn in Russia before relocating to the United States in 2000. She completed her internal medicine internship at the University of Nevada and her residency at a Stanford-affiliated program in Santa Clara, California.

Deeply interested in the impact of lifestyle on both physical and mental health, Johnsen transitioned her focus toward prevention-based care after witnessing how many chronic conditions could be avoided or improved through lifestyle interventions. She became board-certified in lifestyle medicine in 2021 and further expanded her expertise by earning board certification in obesity medicine in 2025.

Johnsen is passionate about empowering patients with evidence-based tools to achieve sustainable health and long-term well-being.

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Valencia Higuera

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Valencia Higuera is a writer and digital creator from Chesapeake, Virginia. As a personal finance and health junkie, she enjoys all things related to budgeting, saving money, fitness, and healthy living. In addition to Everyday Health, Higuera has written for various publications, including Healthline, GOBankingRates, MyBankTracker, and The Mortgage Reports.
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Resources
  1. Herpes: HSV-1 and HSV-2. Johns Hopkins Medicine.
  2. Cold Sore: Symptoms and Causes. Mayo Clinic. January 5, 2024.
  3. Cold Sores: Signs and Symptoms. American Academy of Dermatology.
  4. Ludmann P. Cold Sores: Diagnosis and Treatment. American Academy of Dermatology. February 1, 2024.
  5. Cold Sores (HSV-1). KidsHealth. February 2019.
  6. Cold Sore. NHS Inform. December 5, 2023.