A fever blister typically heals completely within 5 to 15 days, with most outbreaks resolving closer to the 10-day mark. The timeline depends on whether it’s your first outbreak or a recurrence, whether you treat it early, and how well your immune system responds. First-time outbreaks tend to last longer and feel more severe, while recurring sores often follow a predictable pattern that gets shorter over time.
The Five Stages of Healing
Every fever blister moves through the same sequence, and knowing where you are in the process helps you estimate how many days remain.
The first stage is a tingling, burning, or itching sensation on or near your lip. This prodrome phase lasts several hours to about one day before anything is visible. It’s the best window to start treatment, because antiviral medication is most effective before a blister forms.
Next, a cluster of small, fluid-filled blisters appears. These typically surface within 24 hours of the tingling and may grow or merge over the next day or two. Around 48 hours after the blisters form, they rupture, ooze fluid, and leave a shallow, raw sore. This weeping stage is often the most painful and lasts roughly three days. It’s also the period when the sore is most contagious.
A yellowish crust then forms over the open sore. This scab may crack, bleed slightly, or itch as the skin underneath rebuilds. Resist the urge to pick at it, since peeling the scab off can introduce bacteria and cause scarring. The crust stage usually lasts two to three days before the scab naturally falls away, revealing healed (sometimes slightly pink) skin beneath.
When You’re Contagious
A fever blister becomes contagious before you can even see it. The virus can spread starting one to two days before the sore appears, as soon as that first tingle begins. It remains transmissible throughout the entire outbreak, with the highest risk during the weeping stage when fluid is leaking from open blisters. The contagious window can last up to 15 days total. Once the skin has fully cleared with no visible sore or scab, transmission through that site is no longer possible.
During an active outbreak, avoid kissing, sharing utensils or lip products, and touching the sore with your fingers. If you do touch it, wash your hands immediately to avoid spreading the virus to your eyes or other parts of your body.
How Treatments Affect Healing Time
No treatment eliminates a fever blister overnight. Even the most effective options only shorten an outbreak by roughly one to two days. That said, starting treatment early, during the tingling stage, makes the biggest difference.
Prescription antiviral pills work from the inside out and are the fastest option. Your doctor can prescribe a short course that you begin at the first sign of tingling. Some people who get frequent outbreaks keep a prescription on hand so they can start immediately.
The most widely available over-the-counter option is a cream containing 10% docosanol (sold as Abreva). In a clinical trial of over 700 patients, those using docosanol healed in a median of 4.1 days, which was about 18 hours faster than those using a placebo cream. That’s a modest benefit, but it adds up when you’re counting the hours until a sore is gone. For best results, apply it five times a day starting at the first tingle.
Pain relief matters too. An over-the-counter pain reliever can take the edge off, and topical creams with a numbing agent help with the soreness during the weeping and crusting stages.
Does Lysine Actually Help?
Lysine supplements are one of the most popular natural remedies for fever blisters, but the clinical evidence is mixed. Multiple randomized controlled trials have found no significant difference in healing time between people taking lysine and those taking a placebo. Whether the dose was 1 gram per day or over 2.5 grams per day, the sores didn’t heal any faster.
Where lysine shows more promise is in prevention. Several studies found that people taking lysine supplements experienced fewer outbreaks per year, particularly at doses above 1 gram daily. Higher doses (above 3 grams daily) also seemed to improve how the disease felt subjectively, even if the sores didn’t disappear sooner. So lysine may be worth considering as a daily preventive measure, but it won’t speed up an active blister.
Common Triggers That Start an Outbreak
Fever blisters are caused by herpes simplex virus type 1 (HSV-1), which infects roughly 64% of people worldwide under age 50. After a first infection, the virus retreats into nerve cells near the base of the skull and stays dormant until something reactivates it. Knowing your triggers can help you prevent outbreaks or at least catch them early.
Sun exposure is one of the most well-documented triggers. UV light can reactivate the virus from its dormant state in nerve tissue, with sores typically appearing about five days after significant sun exposure. Wearing lip balm with SPF year-round is a simple way to reduce this risk. Other common triggers include fever or illness (which is where the name “fever blister” comes from), physical or emotional stress, hormonal changes during menstruation, fatigue, and cold or windy weather that dries and damages the lips.
Signs of a Complication
Most fever blisters heal on their own without any lasting effects. But if a sore lasts longer than 15 days, something else may be going on. A secondary bacterial infection is the most common complication. Watch for increasing redness spreading beyond the sore’s border, pus replacing the normal clear fluid, or a fever developing alongside the blister. These signs mean bacteria have colonized the open sore, and you’ll likely need a different type of treatment to clear the infection.
People with weakened immune systems, from chemotherapy, organ transplants, or conditions like HIV, can experience more severe and longer-lasting outbreaks that don’t follow the typical timeline. Fever blisters that spread to the eyes are also a concern and can affect vision if untreated.