I mentioned in a previous post that canker sores are not to be confused with cold sores. This would probably be easier to do if I mentioned what a cold sore is and looks like.

Here is a definition of cold sore from the National Institute of Health.
Herpes labialis is an infection caused by the herpes simplex virus. It leads to the development of small and usually painful blisters on the skin of the lips, mouth, gums, or lip area. These blisters are commonly called cold sores or fever blisters.
This is a virus and is contagious. It can spread by touch or by someone touching the infected area or by contact with anything which has become infected(such as a hand, a towel, razor, tweezers).

Part of the treatment of cold sores includes ensuring you don’t spread the virus to others or other parts of your own body.

Wash blisters gently with soap and water to reduce the spread of the virus to other areas of skin. An antiseptic soap may be recommended. Applying ice or warmth to the area may reduce pain.

The warning signs of cold sores are:

Skin lesions or rash around the lips, mouth, and gums
Small blisters (vesicles) filled with clear yellowish fluid
Blisters on a raised, red, painful skin area
Blisters that form, break, and ooze
Yellow crusts that slough to reveal pink, healing skin
Several smaller blisters that merge to form a larger blister
Mild fever (may occur)
If the symptoms do not go away in a week or two you should see your doctor.