Lip herpes, commonly called cold sores or fever blisters, appears as a cluster of small, fluid-filled blisters that form on or around the lips. They typically show up along the border where the lip meets the surrounding skin, though they can also appear near the nose or on the cheeks. The look of a cold sore changes significantly over 1 to 2 weeks as it moves through distinct stages, from a barely visible swelling to an open sore to a crusty scab.
What Each Stage Looks Like
A cold sore doesn’t appear all at once. It progresses through a predictable sequence, and knowing what to expect at each phase helps you identify one early.
Prodrome (several hours to one day): Before anything is visible, you’ll feel tingling, burning, or itching on a specific spot of your lip. The skin may look slightly pink or swollen, but there’s no blister yet. Some people also feel tired, achy, or mildly feverish during this phase, especially during a first outbreak.
Blister formation (days 1 to 2): A small, hard, painful bump appears and quickly develops into one or more tiny blisters filled with clear fluid. These blisters tend to cluster together in a patch rather than appearing as a single sore. They’re often the size of a pencil eraser or smaller, and the skin around them looks red and inflamed.
Oozing and crusting (days 2 to 4): The blisters merge, burst open, and leak fluid. This is the stage that looks the most alarming. You’ll see shallow, wet, reddish sores where the blisters used to be. After roughly 48 hours, the open sores begin to dry out and form a yellowish or brownish crust.
Scabbing and healing (days 4 to 15): A hard scab covers the sore. It may crack, bleed slightly, or itch as the skin underneath repairs itself. The scab eventually falls off on its own, revealing healed pink skin that returns to its normal color over the following days. Cold sores typically disappear fully within 5 to 15 days.
Where Cold Sores Typically Appear
The most common location is right along the edge of the lips, where the red lip tissue meets the surrounding skin. They almost always form on the outside of the mouth, not inside it. Occasionally, blisters show up just below the nose, on the chin, or on the cheek. They tend to recur in the same spot or close to it each time, because the virus lives in a specific nerve cluster and travels the same pathway to the skin surface.
People with oral herpes caused by HSV-1 experience recurrences at an average rate of about once every 8 to 9 months, though this varies widely. Some people get outbreaks several times a year, while others go years between them.
How Cold Sores Differ From Canker Sores
This is one of the most common mix-ups. Canker sores are round, white or yellowish ulcers with a red border that form inside the mouth, on the gums, inner cheeks, or tongue. They are not caused by a virus and are not contagious. Cold sores, by contrast, are clusters of small fluid-filled blisters that form on the outside of the mouth, around the lips. If you see a single round sore inside your mouth, it’s more likely a canker sore. If you see a patch of tiny blisters on or near your lips, that’s the hallmark appearance of herpes.
Conditions That Look Similar
A few other conditions can mimic the appearance of lip herpes, especially in the crusting stage.
Impetigo is a bacterial skin infection that also causes blisters around the mouth and nose. The key visual difference is the crust: impetigo produces a distinctive honey-colored, golden-yellow crust over weepy sores, while cold sore scabs tend to be darker brown or reddish. Impetigo sores also don’t cluster in the same tight patch that cold sores do and may appear on other exposed skin like the arms or legs.
Angular cheilitis causes cracking, redness, and sometimes blistering at the corners of the mouth specifically. People often confuse it with cold sores, but angular cheilitis is not caused by a virus and is not contagious. It results from moisture buildup, yeast, or nutritional deficiencies. If the irritation is limited to the corners of your mouth and looks more like cracked, soggy skin than fluid-filled blisters, angular cheilitis is the more likely explanation.
When a Cold Sore Looks Infected
Cold sores occasionally develop a secondary bacterial infection. Signs that something beyond normal healing is happening include spreading redness around the sore that keeps expanding, pus replacing the usual clear fluid inside the blisters, increased pain or warmth at the site, and fever. A normal cold sore stays roughly the same size and follows the predictable progression from blister to scab. If the redness is growing outward or the crusting turns thick and greenish-yellow, that suggests bacteria have moved in.
When the Sore Is Contagious
A cold sore is contagious from the very first moment you feel tingling until the scab has completely fallen off and the skin looks normal again. The highest risk of spreading the virus is during the oozing stage, when the blisters have burst and are leaking fluid. That fluid is packed with active virus. Kissing is safe again only after the sore has fully healed, which takes anywhere from 5 to 15 days.
One important detail: the virus can also spread when no sore is visible at all. About 60% of people with oral herpes shed the virus at times without developing blisters, particularly during what would otherwise be the prodrome phase. This is why herpes is so widespread, with most adults carrying HSV-1 whether or not they’ve ever had a visible cold sore.