The National Library of Medicine (NLM) describes cold sores as blisters on and around the lips. The blisters are often called fever blisters, but it should not be confused with canker sores. The virus that causes the cold sore is the herpes simplex virus type I, according to the NLM. The infection is contagious and can occur repeatedly. Kissing and sharing items that touch the effected areas spreads the virus from person to person. Treatment is not necessary, but it may help to diminish the symptoms associated with the virus. There are both over-the-counter and prescription medications available for use.
Before the Blister
Before the cold sore blisters even appear signs of an outbreak may be evident. Over time, individuals may learn to recognize the pre-blister symptoms. According to the NLM, this stage of the cold sore is called the prodrome or tingling stage. Some individuals may not experience some or all of these early symptoms. Possible early signs include: tingling, itching, swelling and tenderness at the site of a future cold sore. This stage can last one to two days.
Almost a Blister
Toward the end of the second day the site of the cold sore may become red and more tender to the touch. The tissues may begin to rise up and become more noticeable. Some individuals may already have difficulty moving the mouth without discomfort. The first time an individual contracts the virus a fever may be present without any blisters, according to the NLM.
Blister Stage
By the end of the second day or the beginning of the third, a blister or several blisters may be visible. According to the Mayo Clinic, the cold sores appear as small, painful, red, raised, fluid-filled bumps near the mouth. Some people may experience the blisters along the gums or on the roof of the mouth, explains the Mayo Clinic. Sores on the tongue, under the tongue, or on the inner cheek are not associated with cold sores, but may be a canker sore.
Once the blister forms, it will last about two days before bursting and becoming an open wound. This stage is called the ulcer stage, according to the NLM. Once the blister opens, it will form a scab and heal completely within two to four days.
