Detailed side-by-side comparison
Canker sores and cold sores are frequently confused, but they are completely different conditions with different causes, locations, and treatments. Canker sores (aphthous ulcers) are small, painful ulcers that occur inside the mouth on soft tissues like the cheeks, gums, tongue, and soft palate. Cold sores (fever blisters) are fluid-filled blisters caused by the herpes simplex virus (HSV-1) that appear on or around the lips. Knowing which type you have is essential for choosing the right treatment and understanding whether you might be contagious.
| Factor | Canker Sore | Cold Sore |
|---|---|---|
| Location | Inside the mouth (cheeks, tongue, gums) | On or around the lips and outside of mouth |
| Appearance | Round/oval ulcer with white/yellow center, red border | Cluster of small fluid-filled blisters |
| Cause | Unknown; stress, injury, foods, immune factors | Herpes simplex virus type 1 (HSV-1) |
| Contagious | No, never contagious | Yes, highly contagious when blisters are present |
| Healing Time | 1 - 2 weeks (minor); up to 6 weeks (major) | 2 - 4 weeks without treatment |
| Recurrence | May recur; unpredictable triggers | Recurs; virus remains dormant in nerve cells |
| Treatment | OTC topical pastes, salt water rinses, prescription rinses | Antiviral creams (Abreva), prescription antivirals (Valtrex) |
| Pain Level | Moderate to severe, especially when eating | Moderate; tingling/burning before blisters form |
| Prevention | Avoid trigger foods, manage stress, gentle brushing | Antivirals, avoid triggers (sun, stress), avoid contact during outbreaks |
| When to See Doctor | If lasting over 3 weeks, very large, or recurring frequently | If outbreaks are frequent (6+/year), near eyes, or immunocompromised |
Correctly identifying whether you have a canker sore or cold sore is the most important first step, as the treatments are completely different. Location is the easiest way to tell them apart.
Painful white ulcer on the inside of your cheek after biting it
This is a canker sore. Rinse with salt water, use OTC topical paste (Orajel, Benzocaine), and it should heal within 1-2 weeks.
Tingling sensation on your lip followed by a cluster of blisters
This is a cold sore. Apply Abreva (docosanol) at the first sign of tingling for best results, or ask your doctor for prescription antiviral medication.
Recurrent cold sores more than 6 times per year
Ask your doctor about daily suppressive antiviral therapy (Valacyclovir) to reduce outbreak frequency by up to 80%.
Large, extremely painful sore inside mouth lasting more than 3 weeks
See your dentist. This could be a major canker sore, but persistent oral ulcers should be evaluated to rule out other conditions.
Cost estimates and treatment information shown above are based on national averages in the United States and are for informational purposes only. Actual costs vary significantly based on geographic location, provider, case complexity, and insurance coverage. This comparison is not a substitute for professional dental advice. Always consult your dentist to determine the best option for your individual needs. Read our full Medical Disclaimer.