Cold sores / Fever blisters - Stages | Identification | Pictures | Signs & Symptoms.

Links to images.
Link to cold sore stages slideshow.
Link to cold sore locations slideshow.

Cold sores (fever blisters) are usually distinguished from other types of mouth sores by way of evaluating:

  1. The way the sore looks as it goes through its stages of formation.
  2. The location in which the lesion forms.
  3. Laboratory testing can be performed but is not commonly used or needed.

(Scroll on down this page for pictures and details.)

A) What do cold sores look like? (The 5 stages.)

The appearance of a cold sore (fever blister) will gradually change as it progresses through the five stages of formation outlined below.

The timeline for this transformation (from first sign to complete healing) usually lasts between 8 and 12 days.

FYI: The stage of your sore correlates with its level of contagiousness.

1) The Tingle stage (Prodrome stage) - days 1 & 2.

In most cases, a person's first indication that they have a cold sore starting to form is that they notice a new sensation (burning, stinging, itching, soreness, tautness, or swelling) in the area where the lesion will ultimately appear.

What to look for - The area may become reddened, and slightly raised or elevated (papule formation).

Things to know - All of these initial symptoms are signs of inflammation. (Your body's response to the herpes virus and the tissue damage it's starting to cause.)

Slide show of the stages of cold sore formation.

The stages of cold sore (fever blister) formation.

2) The Blister stage - days 2 & 3.

The first readily visible sign of cold sore formation is the appearance of multiple fluid-filled blisters.

What to look for - The blisters are usually very tiny (smaller across than the thickness of a dime). And form in a cluster that's no larger than about the size of a nickel. In some cases, individual blisters may join together to form a single larger one.

Things to know - This is the stage where the total number herpes virions (virus particles, HSV) is the greatest. The overall size of the forming lesion generally correlates with the relative number of virions present. (Hull 2014) [page references]

In about 25% of cases, the herpes infection is brought under control (either just by your body's immune system or with the help of antiviral medication) before blisters can develop. Since no blisters or following ulceration form, these are sometimes referred to as "failed" or "aborted" lesions. (Opstelten 2008)

3) The Weeping stage (Ulcer stage) - day 4.

The blisters usually rupture soon after they've appeared. As they do, they release a clear fluid teeming with herpes virions. After all have broken, the sore transforms into an ulceration.

What to look for - Immediately after rupture, the lesion starts off as a shallow red ulcer (a wet, raw looking sore) whose surface then turns grey.

Things to know - This phase of fever blister formation can be the most painful stage, and the one during which it's most contagious.

By this point, the replication rate of the virus has passed its peak. And the inflammation reaction triggered by the presence of the virions and damage to skin cells they have caused is in full swing as it continues to clean up the carnage. It's this inflammation response (a part of the normal healing process) that's responsible for redness, swelling and tenderness associated with cold sores as they continue through their stages.

4) The Crusting stage - days 5 through 8.

If the ulcer has formed in a location where it's not kept wet by moisture from the mouth, it will scab over.

What to look for - The scabbing looks like a yellow, or dark red to brownish, crust. It often cracks or breaks, which results in bleeding.

During times when a scab has come off, you can see the amount of ulceration that still remains and the pink, newly formed tissue that surrounds it.

Things to know - The formation of the scab is often accompanied by an itching or burning sensation. Moisturizing the scab can help to prevent this

5) The Final Healing stage - days 9 through 12.

As time progresses, so will the sore's healing.

What to look for - A series of scabs will usually form on the lesion with each one flaking off before it's replaced by a new one.

Each new scab will be smaller than the previous one, until finally the lesion resolves fully and in most cases without scarring.

The locations where cold sores form.

Locations where cold sores (fever blisters) form.

B) Where do cold sores form?

Cold sores form either:

  • On or at the edge of the lip.
  • On the face, near the mouth. This can include the lower portion of the nose.

Cold sores typically form in generally the same location as they have during previous outbreaks. Here's why.


C) Are cold sores contagious?

Yes, during times when you have a cold sore spreading the herpes virus to others should be a concern.

Cold sores, the liquids coming from them and even your own saliva can transfer virions to other people, or even other parts of your own body (see below).

1) Transmission to others.

a) Direct contact.

One common route by which the herpes virus is transmitted to other people is via direct skin-to-skin contact. This can include activities like kissing, or even just touching your sore against someone's face during a hug.

  • It's best practice to refrain from being intimate with others or participating in contact activities (e.g. wrestling, basketball) while you have a sore. (See below for which stages tend to release the most virus particles.)
  • Research suggests that the transmission of HSV during periods of asymptomatic viral shedding is more common and more significant than previously thought. (Asymptomatic = No apparent lesion exists.)

    One study monitored healthy herpes positive (HSV 1) subjects. It detected asymptomatic oral shedding on 12% of days, with an average duration of 24 hours for each episode. (Mertz 2008)

The difficulty associated with asymptomatic viral shedding in terms of prevention of transmission is that the infected person is unaware that the event is occurring.

b) Via an intermediary.

Virus particles can also be transmitted to others by way of intermediary objects that have touched your sore or saliva.

  • Avoid sharing articles like an eating utensil, cup or glass, or items such as a razor, bar of soap, lipstick or lip balm applicator, toothbrush, or towel.
  • Properly dispose of items used to apply medicines to or treat cold sores.
c) Other precautions.

Some people are at greater risk than others for complications associated with herpetic infections. And for this reason they should be given special consideration. This includes people with either immature immune systems (newborn babies) or compromised ones (such as chemotherapy or HIV patients).

2) Transfer to other body parts.

Always wash your hands after treating your fever blisters.

Always wash your hands after touching a cold sore.

Besides just oral infections, it's important to understand that the herpes virus can also cause infections in other body parts. And this includes your own body, not just others.

  • Herpes simplex can cause herpetic whitlow, a painful infection of the fingers.
  • A herpes infection of the eye can result in corneal blindness.

    If you wear disposable contact lenses and contamination is suspected, then throw them away. To avoid this issue, you may choose to wear your glasses when you have a cold sore.

  • Being intimate with others can cause infection of your partner's genitals.
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3) When are cold sores the most contagious?

Virus particles are present during all stages of cold sore formation. And for that reason, each and every stage should be considered to be contagious.

a) Wet lesions are the worst.

The most contagious stage of a cold sore is when its blisters rupture (the Weeping stage). This is because the liquid contained in these blisters holds literally millions of herpes simplex virions.

b) Scabbed lesions, less so.

As a cold sore continues to run its course, the number of virus particles present in it diminishes. Usually by the time a scab has formed (the Crusting stage) the number of virus particles has lessened dramatically.

4) Other best practices for preventing viral spread.

  • Besides just when treating a sore, wash your hands (soap and water) repeatedly throughout the day.
  • Don't touch or pick at cold sores. Only touch them when treating them.
  • Dab medication on a lesion rather than rubbing it in, so not to disturb the sore.


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