Canker Sore vs. Cold Sore: Key Differences and How to Treat Them

If you have a painful spot in or around your mouth, you may be wondering if it is a canker sore or a cold sore. The most reliable way to distinguish them is by location: canker sores occur inside the mouth, while cold sores typically appear on or around the lips. Understanding the differences in these conditions is essential to help you determine your next steps for treatment.

1. Appearance and Location

The first way to differentiate a canker sore vs. cold sore is by appearance. Canker sores, or aphthous ulcers, develop on soft tissues inside the mouth, such as the gums, tongue, or inner cheeks. They appear as small, round, white or yellow lesions with a distinct red border. In contrast, a cold sore often looks like a cluster of blisters, and they can eventually burst, causing oozing and crusting. Clinical note: Canker sores are non-keratinized lesions, meaning they form on the soft, movable lining of the mouth, whereas cold sores are typically found on keratinized tissue like the outer lip.

2. Causes and Triggers

Canker sores and cold sores have different underlying causes. According to the American Dental Association, the exact cause of canker sores is unknown. Conversely, cold sores result from the herpes simplex virus (HSV). This virus is dormant until triggered, which is when you might experience a tingling or burning sensation in your mouth and the development of a sore. Triggers include stress, fatigue, fever, other viral infections, exposure to sun or wind, and hormonal changes.

3. Treatment and Professional Care

Most minor canker sores heal within one to two weeks, while cold sores may take two to four weeks. Cold sores usually do not leave scars; however, major canker sores have the potential to cause scarring. If your symptoms last longer than you’d like, you can discuss treatment options with a medical or dental professional. For canker sores, if they are unusually large, clustered, or painful, your doctor or dentist may suggest mouthrinses, topical ointments, or oral medication. According to the American Academy of Dermatology (AAD), cold sores are treated with antiviral topical or oral medications. If you are experiencing discomfort, your doctor or dentist may also prescribe a pain-relief medication. The AAD also encourages using sunscreen during an outbreak, as sun exposure can affect healing. Find resources, products, and information to give your patients a healthier future.

Frequently Asked Questions

Are canker sores contagious?

No, canker sores are not contagious. However, because cold sores are caused by HSV, they are contagious. To prevent spreading the virus, you should not share utensils or any other items that touch the mouth.

When should I see a professional?

If your symptoms last longer than you’d like, you can discuss treatment options with a medical or dental professional. Seek evaluation if the sores are unusually large, clustered, or painful. Red flag: Consult a professional if you experience a high fever, difficulty swallowing, or if the sore persists beyond two weeks without signs of healing.

Do these sores leave scars?

Cold sores usually do not leave scars, but major canker sores have the potential to cause scarring. Clinical note: Major canker sores are defined as those larger than 10 millimeters in diameter and may take up to six weeks to heal.