Cold sores, also known as fever blisters, are small, fluid-filled blisters that usually appear in clusters on or around the lips. They may also show up on the chin, cheeks, or nose. These sores are caused by the herpes simplex virus (HSV), a highly contagious virus that spreads through close contact or sharing items such as utensils or lip balm with someone having an active outbreak.

Once infected, the virus remains dormant in the body's nerve cells and can reactivate due to triggers like stress or illness. Not everyone with HSV will develop cold sores, but for those who do, symptoms and frequency can vary widely.

Common Symptoms

Cold sore symptoms typically follow a five-stage progression:

  • Tingling (prodrome)

  • Blistering

  • Oozing

  • Crusting

  • Healing

Most cold sores heal within 7 to 15 days. The first outbreak may be accompanied by flu-like symptoms such as fatigue, body aches, headache, fever, and swollen lymph nodes. Recurrent outbreaks are usually milder and shorter in duration.

Stage 1: Tingling

This is the earliest stage, also called the prodrome stage. You may feel a tingling, itching, or burning sensation in the area where a sore is about to form. The skin might feel sore or sensitive to the touch. This stage lasts from a few hours to a day before blisters appear.

Stage 2: Blistering

Small fluid-filled blisters begin to form in the affected area. These may be painful and often cluster together. The skin around the blisters may become red and swollen. The blisters grow over the next two to three days and are highly contagious during this stage. Avoid kissing or sharing items, and wash your hands immediately if you touch the sore.

Stage 3: Oozing

The blisters burst, releasing a clear or yellowish fluid and leaving shallow, open sores with red borders. This is often the most painful stage and typically lasts two to three days. The risk of spreading the virus is still very high, and the area should be kept clean to avoid secondary bacterial infections.

Stage 4: Crusting

The open sores begin to dry out, forming a yellowish crust that later turns into a brown scab. This scab acts as a protective layer over healing skin. It may crack or bleed, causing soreness and itching. Avoid picking the scab to prevent scarring and delayed healing.

Stage 5: Healing

The scab naturally falls off, revealing new skin beneath that may look pink or dry for a few days. This final stage usually lasts about two days. Most cold sores heal completely without leaving scars.

When to See a Healthcare Provider

While cold sores usually resolve on their own within 7 to 15 days, you should consult a healthcare provider if:

  • You have a weakened immune system

  • Sores do not heal after two weeks

  • You experience frequent outbreaks (more than three times a year)

Seek immediate attention if you have:

  • Sores near or inside the eyes

  • Eyes that feel gritty or sensitive to light

  • High fever

  • Pus or spreading redness near the sore

A Quick Review

Cold sores are painful, fluid-filled blisters caused by the herpes simplex virus. They develop in five stages: tingling, blistering, oozing, crusting, and healing. Cold sores are contagious throughout all stages. While most heal naturally, recurring or severe cases may require medical care. Prevent spreading the virus by avoiding direct contact and practicing good hygiene during flare-ups.