Cold sores, also known as fever blisters, are a common infection appearing as small, painful blisters on or around the mouth. They are caused by the herpes simplex virus type 1 (HSV-1), a contagious virus that remains in the body for life once acquired. While many people carry the virus, not everyone experiences symptomatic outbreaks. The virus spreads through close contact, such as kissing, or by sharing items like eating utensils, towels, or lip balm.
Appearance of Cold Sores Inside the Mouth
Cold sores inside the mouth follow stages. The initial indication involves a tingling, itching, or burning sensation where the sore will develop, known as the prodromal stage. This sensation can occur a day or two before any visible signs appear, signaling that the virus has reactivated in the nerve cells.
Small fluid-filled blisters emerge within 24 hours. These blisters are grouped in clusters, appearing on a red, swollen base. The fluid inside these blisters is contagious, and the surrounding tissue becomes discolored, swollen, and painful.
After one to two days, these blisters break open, releasing fluid, a stage sometimes called the “weeping phase.” This leaves behind shallow, painful open sores or ulcers. Within days, these open sores dry out, forming a golden-brown crust or scab as they heal. The scab may crack or bleed but falls off within six to 14 days. The underlying skin returns to normal within one to two weeks.
Common Locations for Oral Cold Sores
While cold sores often appear on the lips and skin around the mouth, they can also appear inside the mouth, especially during a primary infection. Common intraoral sites include the hard palate, which is the roof of the mouth, and the gums. The tongue and inside of the cheeks can also be affected.
During an initial outbreak, especially in young children, sores can be widespread throughout the mouth and throat, a condition known as herpetic gingivostomatitis. This leads to painful blisters and ulcers on the tongue, gums, and other oral mucous membranes. Recurrent cold sores inside the mouth often appear in the same locations each time.
Distinguishing Cold Sores from Other Mouth Sores
Differentiating cold sores from other oral lesions, such as canker sores, is important for management. Cold sores are caused by the herpes simplex virus (HSV) and are contagious, especially when blisters are present and oozing fluid. They appear as clusters of small, fluid-filled blisters on fixed tissues like the gums or hard palate.
Canker sores are not caused by a virus and are not contagious. They appear as single, round or oval ulcers with a white or yellowish center and a red border. Unlike cold sores, canker sores form on movable tissues inside the mouth, such as the inside of the lips, cheeks, or under the tongue. They are often painful and can be triggered by factors like stress, injury, or nutritional deficiencies.
When to Consult a Healthcare Professional
While cold sores often heal on their own, there are situations when medical advice is beneficial. Consulting a healthcare provider if a cold sore has not started to heal within 10 days to two weeks. Persistent sores, those that are unusually large or cause severe pain, warrant professional evaluation.
Individuals experiencing frequent recurrences of cold sores can benefit from prescription antiviral medications to reduce the frequency and severity of outbreaks. If there are signs of a bacterial infection, such as spreading redness, pus, or fever, medical attention is necessary. People with weakened immune systems, due to conditions like HIV or cancer, should consult a doctor if they develop a cold sore, as infections can be more severe and lead to complications.