There are 5 stages of cold sore. These are tingle stage, blister stage, ulcer stage/weeping stage, crusting stage/ scabbing stage and healing stage. Cold sore lasts for 8-10 days but in some cases, it may last for 2weeks. Ulcer stage which is also known as weeping stage is the most painful and contagious of all the stages.

EARLY STAGE/ TINGLE STAGE/PRODROME STAGE: This stage lasts for few hours or 1-2days. It is hardly even noticed. In this stage, a person feels a tingling or a burning sensation. That is why it is also known as tingle stage. Before it becomes visible, the skin starts getting tightened in the area where the cold sore is about to be formed. Due to the infection, inflammation occurs and that area becomes red and swollen. The infection can spread even at this stage so the patient should avoid any kind of physical contact. This marks the first stage of the cold sores as the virus is heading towards the outer surface layer of the neural tissue cells.

BLISTER STAGE:The cold sore blister appears in the region within twelve to thirty six hours. The first sign which is seen is a fluid filled blister which is very small in size and they usually form in a cluster. Individual blisters may coalesce with others to form a single larger blister.

The patient will see the swelling at the fever blister site along with the development of little, hard and pimple-like protuberances that are highly painful. Fever, headaches and a general feeling of tiredness is common to notice at this stage. Lymph glands present under the jaw also begin to swell. White blood cells which fights the infections of the body travel to the blister. These cold sore blister contains millions of virus particles. This stage lasts from 2nd to 4th day.
ULCER STAGE/ WEEPING STAGE:

The tiny hard elevations now swell, burst open and coalesce to make up a huge open up ulcer. Its surface becomes gray. A ring of inflammation which is red in color can be seen around the area which is affected. Fever, running nose and head pains are other common symptoms associated with this point of the stage. This part is the most painful time of this stage. This is the most contagious stage. The lymphatic nodules are quite well edematous as felt under the surface of the lower jaw which might be quite painful. This stage is seen on day 4.
CRUSTING / SCABBING STAGE:


In this stage, the ulcer becomes dry and will scab in the areas where the lesion is not kept moist by the saliva from the oral cavity. It will scab over with a brownish crush and is accompanied by itching or burning sensation. The scab may crack which further causes bleeding. This stage can be seen from day 5 to day 8.
HEALING STAGE:

In the healing stage, a number of scabs are formed on the lesion which subsequently flakes off. Every new scab will be shorter than the earlier one. And finally the cold sore will resolve completely. Frequently no scar formation occurs. The skin may remain slightly pink or red.The symptoms like headaches, fever and edematous lymph glands start healing by now. Itching and irritation of the cold sore are still experienced even though the healing process continues. This stage can be seen from day 9-day12. Healing continues underneath the new skin which is a constant source of tingling and redness present in the area for another week or more. This stage of the cold sore is still infectious and can cause them to re-occur very fast. The body temperature and the head pains are nearly gone by this time. The swollen lymphatic nodules are greatly decreased by this time.
While still in the final stage of their life cycle the fever blister can tend to come back. This time is perfect to use your best cold sore treatment at this stage. The fever blisters can easily spread from one person to another or from one part of the body of the infected person to another site in the same patient.
Pay attention and be careful as the cold sore virus is very infectious from the first irritation the complete absence of the fever blister signs and symptoms.
Cold sores are not just restricted to the mouth and lips but can also occur on nose, eyes and even hands.

Picture of Cold Sore on the nose