A cold sore is a skin lesion on the lips or around the mouth caused by infection with the herpes simplex virus (HSV). Cold sores typically progress through five stages: prodrome, blister, ulcer, crusting, and healing. The cold sore lifecycle from initial infection to complete healing usually lasts 7-12 days.
What causes a cold sore?
Cold sores are caused by infection with the herpes simplex virus (HSV). There are two types of HSV: HSV-1 and HSV-2. HSV-1 is the usual cause of cold sores around the mouth, while HSV-2 typically causes genital herpes. However, either virus can infect either location.
Many people get infected with HSV-1 in childhood. The virus remains dormant in nerve cells and can reactivate later, leading to cold sores. Triggers for recurrence include:
- Fever
- Stress
- Sun exposure
- Changes in hormone levels
- Menstruation
- Illness
- Skin damage
Once a person is infected, the virus stays in their body forever. Outbreaks may recur throughout life.
What are the stages of a cold sore?
Experts divide the cold sore lifecycle into five main stages:
- Prodrome
- Blister
- Ulcer
- Crusting
- Healing
Let’s look at each stage in more detail:
Stage 1: Prodrome
The prodrome stage is the first warning of an impending cold sore. It starts about 24 hours before a blister appears. Symptoms include:
- Tingling, burning, itching at the site where the sore will develop
- Redness or swelling at the site
- Pain or soreness
- Feeling of tension or tightness in the skin
At this stage, the virus is reproducing and traveling from the nerve ganglion to the skin. No blister is present yet. The prodrome stage usually lasts 1-2 days.
Stage 2: Blister
In the blister stage, fluid fills a lesion at the infection site:
- A red, fluid-filled blister or group of blisters appears
- The blister may be large, tense and painful
- Common sites include the edge of the lips, cheeks, chin, nose, or nostrils
Inside the blisters, HSV particles multiply rapidly. The blister stage lasts 1-2 days.
Stage 3: Ulcer
Next, the blisters break open and weep clear fluid, leaving an open ulcer:
- The blister ruptures, releasing fluid and leaving an ulcer
- The ulcer appears red, wet and painful with a yellowish membrane
- Weeping of clear serum from the ulcer may occur
In the ulcer stage, the cold sore is no longer intact. This stage lasts 2-3 days.
Stage 4: Crusting
After weeping stops, a crust forms over the ulcer:
- Fluid leakage ceases and a brownish crust develops
- The lesion may look dry and crusted with a reddish border
- It may crack or bleed if agitated or picked
In the crusting stage, the cold sore scabs over as it begins healing. This stage lasts 2-3 days.
Stage 5: Healing
Finally, the crust falls off and new skin forms underneath:
- The crust sloughs off, exposing pink regenerating skin beneath
- The skin gradually returns to normal with no scarring
- Some redness may remain at the site
- The lesion heals completely in 1-2 weeks
In the healing stage, the skin renews itself until the cold sore resolves. Healing takes approximately 4-5 days.
What does the timeline look like?
On average, a cold sore runs its course in 7-12 days. But each stage lasts variable amounts of time. Here is an estimated timeline:
| Stage | Duration |
|---|---|
| Prodrome | 1-2 days |
| Blister | 1-2 days |
| Ulcer | 2-3 days |
| Crusting | 2-3 days |
| Healing | 4-5 days |
So the sequence is:
- Tingling and pain for 1-2 days
- Blister forms for 1-2 days
- Blister ruptures, leaving an ulcer for 2-3 days
- Crust develops for 2-3 days
- Crust falls off, healing begins for 4-5 days
But keep in mind every cold sore is unique. Your sore may progress faster or slower than average.
What are the symptoms at each stage?
The symptoms vary at each stage of a cold sore:
| Stage | Symptoms |
|---|---|
| Prodrome | Tingling, burning, pain, soreness, swelling, tightness at site |
| Blister | Fluid-filled blister appears, may be large and painful |
| Ulcer | Blister ruptures leaving red, wet ulcer with yellow membrane |
| Crusting | Brownish crust develops, may crack or bleed if agitated |
| Healing | Crust sloughs off, pink skin forms, gradual return to normal |
Identifying the stage based on symptoms can help guide treatment. Antiviral medication works best when started at the prodrome or blister stage before the sore fully forms.
How long is each cold sore stage contagious?
A cold sore is contagious throughout its whole course, from prodrome through complete healing. However, it poses the greatest risk of transmission during the ulcer and weeping stages when viral shedding peaks. Here is the relative contagiousness timeline:
| Stage | Contagiousness |
|---|---|
| Prodrome | Mildly contagious |
| Blister | Very contagious |
| Ulcer | Extremely contagious |
| Crusting | Moderately contagious |
| Healing | Weakly contagious |
The ulcer stage poses the highest transmission risk when viral shedding and contact with fluids are greatest. But it’s important to remain vigilant about contagion until the sore fully resolves.
How can you tell if a cold sore is starting?
Catching a cold sore in the prodrome stage can allow early treatment. Watch for these early warning signs:
- Tingling, burning, itching – These sensations at the site where the sore will appear are often the first symptoms
- Redness, swelling – The area may become red, inflamed and slightly swollen
- Pain, soreness – Localized pain or tenderness indicates inflammation
- Feeling of tightness – The skin feels taut and stiff as the virus reproduces beneath the surface
If you experience any of these, start antiviral medication immediately. Don’t wait for a blister to form.
What’s the fastest way to get rid of a cold sore?
The fastest way to get rid of a cold sore is to start medication at the first sign of prodrome symptoms before the blister erupts. Antiviral medication can speed healing by:
- Shortening the duration of symptoms
- Reducing pain, discomfort and sensitivity
- Accelerating healing time
- Preventing the sore from worsening
Oral antiviral tablets, topical creams, or combinations can all be effective if applied at prodrome or the blister stage. Using antivirals as early as possible offers the fastest relief.
How can you prevent cold sores from progressing?
To prevent cold sore progression:
- Start antiviral medication early – At the first tingle or prodrome symptom
- Avoid triggers – Stress, sunlight, fever, hormonal changes
- Don’t pick or touch the sore – This slows healing and spreads infection
- Use lip balm and keep lips moist – Dry cracked skin is more prone to outbreaks
- Keep the area clean – Gently cleanse with mild soap and water
- Avoid close contact – Don’t kiss or share items like towels until fully healed
Taking quick action at the prodrome stage can potentially halt progression to blister and ulcer stages.
Can you stop a cold sore from forming after tingle stage?
It may be possible to stop a cold sore from fully forming if treated in the prodrome or tingle stage. At the first sign of tingling, burning, pain, or tightness take these steps:
- Start antiviral medication right away – Valacyclovir or acyclovir
- Apply an antiviral cream – Docosanol or penciclovir
- Take 1000-3000mg of L-lysine supplements daily
- Dab on lemon balm or licorice root cream
- Try a cold sore patch – These can shorten healing time
Antiviral tablets are most effective but topical creams may also disrupt progression if applied at the earliest stages. The goal is to stop viral replication before the blister emerges.
What helps a cold sore heal faster?
To help a cold sore heal faster:
- Antiviral medication like valacyclovir
- Warm compresses to reduce pain and swelling
- Avoiding irritants like citrus, salt or spices
- Petroleum jelly to keep the sore moist
- Avoiding picking, squeezing or popping blisters
- Lip balm with SPF to prevent sun damage
- Oral pain relievers if needed for discomfort
Antiviral medication can accelerate healing time significantly. But even without it, keeping the sore clean, moist and protected can help it resolve faster.
Should you pop a cold sore blister?
No, you should not pop a cold sore blister. Reasons not to pop it include:
- Increases risk of spreading the virus and contamination
- Disrupts healing and causes more irritation
- Exposes the sore to bacteria which can cause infection
- Makes the sore more painful and inflamed
- Can lead to ulcer lasting longer
- Increases risk of scarring after healing
Popping blisters also forces out antibody-rich fluid that helps combat the virus locally. Allow blisters to rupture naturally instead.
Conclusion
In summary, a cold sore typically progresses through five distinct stages: prodrome, blister, ulcer, crusting, and healing. Catching and treating a sore early in the prodrome stage offers the best chance to halt progression. Avoiding known triggers, keeping the area clean, and using antiviral medication can all help shorten the lifetime of a cold sore.