You feel that telltale tingle on your lip or a sting inside your mouth. Is it a canker sore? A cold sore? Or just your body being dramatic?
While they sound similar and both can seriously disrupt your day, canker sores and cold sores are completely differentin cause, treatment, and contagiousness. Misunderstanding them can lead to ineffective treatment—or worse, spreading an infection.
So let’s clear the confusion. Here’s how to tell the difference between canker sores vs. cold sores, what triggers them, and how to manage or prevent the next unwelcome flare-up.
TLDR – Quick Guide
- Canker sores are non-contagious ulcers inside the mouth.
- Cold sores are contagious blisters caused by the herpes simplex virus (HSV-1), usually on or around the lips.
- Canker sores are triggered by stress, injury, or certain foods.
- Cold sores are viral and can be triggered by illness, stress, or sun exposure.
- Treatments vary: cold sores may require antivirals, while canker sores often resolve on their own.
Detailed Breakdown
What Are Canker Sores?
Canker sores, or aphthous ulcers, are small, shallow lesions that appear inside the mouth—on the inner cheeks, tongue, gums, or roof of the mouth.
Key Traits:
- Not contagious
- Round or oval with a white or yellow center and red border
- Painful when eating, drinking, or talking
Common Triggers:
- Stress
- Minor mouth injuries (like biting your cheek or aggressive brushing)
- Food sensitivities (like citrus, spicy foods, or gluten)
- Vitamin deficiencies (especially B12, iron, and folate)
- Hormonal changes
Treatment:
- Rinse with salt water or antiseptic mouthwash
- Use over-the-counter topical pastes like benzocaine (Anbesol, Orajel)
- Avoid trigger foods
- Severe cases may need corticosteroids or prescription mouth rinses
What Are Cold Sores?
Cold sores, also called fever blisters, are fluid-filled blisters that appear outside the mouth, typically on or around the lips.
They are caused by the herpes simplex virus (HSV-1) and are highly contagious—even before the blister is visible.
Key Traits:
- Contagious (spread through kissing, utensils, lip balm, etc.)
- Starts with tingling or burning, followed by blisters that scab over
- May be accompanied by fever, swollen lymph nodes, or fatigue
Triggers:
- Stress or fatigue
- Illness (colds, flu)
- Sun exposure
- Hormonal shifts
Treatment:
- Antiviral creams (like docosanol or acyclovir) work best when applied early
- Oral antivirals (valacyclovir or famciclovir) for more frequent or severe outbreaks
- Keep the area clean, dry, and avoid touching
- Avoid kissing or sharing items during outbreaks
How to Tell Them Apart
Feature | Canker Sores | Cold Sores |
Location | Inside the mouth | Outside the mouth (usually lips) |
Cause | Not viral | Caused by HSV-1 |
Contagious? | No | Yes |
Appearance | Flat, white/yellow ulcer | Blister that crusts |
Treatment | OTC pain relief, mouthwash | Antiviral creams or pills |
Key Takeaways
- Canker sores are internal and not contagious; cold sores are external and highly contagious.
- Treating them correctly means identifying the source—don’t confuse one for the other.
- Cold sores can be managed with antivirals if caught early; canker sores usually heal on their own, but faster with treatment.
- Prevention starts with knowing your triggers: stress, food, injury, or illness.
- If sores are frequent or severe, see your dentist or doctor for a long-term management plan.
FAQs
No. Canker sores aren’t caused by viruses and aren’t contagious.
Avoid kissing, sharing utensils, and touching the sore. Use antiviral cream early for best results.
Yes, though rare. It’s possible to have a canker sore inside the mouth and a cold sore on the lips simultaneously.
No. HSV-1 stays in the body for life, but outbreaks can be controlled and reduced over time.
If you get frequent outbreaks, unusually large sores, or sores that don’t heal within two weeks, seek professional help.