Cold sores, also known as fever blisters, are painful, fluid-filled blisters that typically appear on the lips, cheeks, or tongue. They are most commonly caused by an infection with the herpes simplex virus type 1 (HSV-1). While HSV-1 is extremely common and carried by the majority of adults globally, many people never show symptoms.

Although treatments can help shorten the duration of cold sores, they do not eliminate the virus, which is why some individuals may experience recurring outbreaks. Fortunately, treatment options are available to ease discomfort and support healing during flare-ups.

Types

Cold sores can develop in different areas of the body, including:

  • Around or inside the mouth

  • Around the eyes

  • On the fingers

  • On the genitals

Symptoms

The first sign of a cold sore is often a burning or tingling sensation on the skin where the sore will appear. Once formed, symptoms may include:

  • Fluid-filled blisters, especially around the lips

  • Tingling or itching near the blister

  • Fatigue

  • Swollen lymph nodes

  • Mild fever

In children, symptoms may differ slightly, such as reduced appetite and increased drooling.

Causes

Cold sores are mainly caused by the herpes simplex virus type 1 (HSV-1). After initial infection, the virus settles into the body's nerve cells and can remain dormant for extended periods. During times of physical or emotional stress, the virus may reactivate and trigger a new outbreak.

Common triggers that can lead to cold sore flare-ups include:

  • Fever or illness

  • Prolonged sun exposure

  • Injuries

  • Hormonal fluctuations (e.g., menstruation, pregnancy)

  • Emotional stress

  • Surgery

Diagnosis

A healthcare provider can usually diagnose cold sores based on their appearance. If there’s uncertainty, they may take a sample from the sore and send it for lab testing to confirm the presence of HSV-1 or rule out other infections.

Cold sores are often mistaken for canker sores, which occur inside the mouth and are not contagious, whereas cold sores typically appear outside the mouth and are highly contagious.

Treatment

While there is no cure for HSV-1, several treatments can help reduce the severity and duration of cold sores. Antiviral medications are commonly used to suppress the virus and accelerate healing. These may be available in different forms:

  • Topical: Creams like acyclovir (Zovirax), applied directly to the sore

  • Oral: Pills such as valacyclovir (Valtrex) or famciclovir (Famvir)

  • Intravenous (IV): Injections given by healthcare professionals for severe cases

Additional remedies to relieve discomfort include:

  • Topical pain relievers: Creams containing lidocaine

  • Over-the-counter pain medication: Ibuprofen or acetaminophen

  • Cold therapy: Ice chips or popsicles can soothe the area

For people with frequent outbreaks, long-term antiviral therapy may be recommended.

Prevention

HSV-1 is spread through close personal contact. To avoid spreading the virus during an active outbreak, it’s important not to:

  • Kiss others

  • Share eating utensils, cups, or lip products

  • Engage in oral sex

To prevent flare-ups, limit sun exposure and use lip balms with at least SPF 30.

Related Conditions

Certain medical conditions can worsen cold sore symptoms or make them more difficult to manage, including:

  • Atopic dermatitis (eczema)

  • Autoimmune disorders such as HIV/AIDS

  • Cancer

People with compromised immune systems may need prescription antivirals to manage outbreaks and reduce the risk of further infections.

Living With Cold Sores

Cold sores can be uncomfortable and affect self-confidence due to their visible nature. However, antiviral treatments can help reduce the frequency and severity of outbreaks. Consulting with a healthcare provider can help you find the best approach for managing and preventing cold sores effectively.