Canker Sores vs Cold Sores: A Canadian Guide
Mouth sores can be confusing, painful, and sometimes embarrassing. The most common culprits are canker sores and cold sores—but they’re not the same. This simple guide helps Canadians tell them apart, treat them safely, and know when to get help.
What’s the difference between canker sores and cold sores?
Canker sores (inside your mouth) aren’t contagious and often follow irritation or stress. Cold sores (on or around the lips) are caused by the contagious HSV‑1 virus and can spread through kisses or shared items. Treatments and prevention differ, so knowing which you have matters.
Canker sores (aphthous ulcers): the basics
Canker sores are small, shallow ulcers that appear inside the mouth—on the inside of the lips or cheeks, the tongue, or the soft palate. They’re usually round or oval with a white, yellow, or grey centre and a red border. They can sting, especially with spicy, salty, or acidic foods.
Common triggers
– Minor mouth trauma (biting your cheek, braces irritation, sharp chips)
– Stress or lack of sleep
– Nutrient gaps (low iron, vitamin B12, or folate)
– Hormonal changes
– Certain toothpaste ingredients (like SLS) in some people
– Food sensitivities (e.g., citrus, tomatoes, nuts in some individuals)
About 1 in 5 people get recurrent canker sores at some point. They’re uncomfortable but not contagious and usually heal in 7–14 days.
What helps
– Rinse with warm salt water (1/2 teaspoon salt in a cup of warm water) 2–3 times daily
– Dab a topical gel or patch designed for mouth ulcers (look for benzocaine or barrier films)
– Switch to an SLS‑free toothpaste if your sores coincide with brushing
– Avoid spicy, acidic, or crunchy foods until healing improves
– For frequent sores, ask your dentist about prescription options (e.g., corticosteroid rinses or gels)
Cold sores (fever blisters): the basics
Cold sores are fluid‑filled blisters caused by the herpes simplex virus type 1 (HSV‑1). They usually form on or around the lips (less commonly on the nose or chin). They often start with tingling, itching, or burning for a day, then blister, ooze, crust, and heal over 7–10 days.
Key points
– Contagious: HSV‑1 can spread through kissing, sharing drinks/utensils, or skin contact with an active sore.
– Triggers for flare‑ups: stress, fatigue, colds/fevers, sun/wind exposure, and dry, cracked lips.
– Many adults carry HSV‑1 even without obvious symptoms; outbreaks vary widely.
What helps
– Start an over‑the‑counter antiviral cream (e.g., docosanol) at the first tingle for best results
– Keep the area clean, moisturized, and protected from sun (use lip balm with SPF)
– Don’t pick at crusts—let them heal naturally
– For frequent or severe outbreaks, talk to your dentist or family doctor about prescription antivirals
Is it contagious? A quick way to tell
– Canker sores: not contagious, inside the mouth
– Cold sores: contagious, usually on or just outside the lips
If you’re not sure, consider location and history: recurrent lip blisters that start with tingling are more likely cold sores.
Home care you can start today
For canker sores
– Rinse with salt water or a baking‑soda solution (1/2 tsp baking soda in a cup of warm water) for comfort
– Consider a soft‑bristled brush and SLS‑free toothpaste
– Use a protective oral patch or gel before meals
– Reduce friction from braces/wires with orthodontic wax
For cold sores
– Start an antiviral cream at the first sign of tingling
– Keep lips moisturized and protected with SPF balm
– Avoid close contact, sharing drinks/utensils, or touching the sore
– Cool compresses can help with soreness
When a sore might be something else
Not every sore is a canker or a cold sore. A sore that doesn’t heal, keeps bleeding, or looks unusual needs professional attention. Dentists in Canada routinely check soft tissues for signs of concern during exams—and can refer you promptly if needed. Learn why early checks matter in oral cancer screening.
“Any mouth sore that lasts more than two weeks should be examined by a dentist.” — Canadian Dental Association
When to see a dentist or doctor in Canada
Book an appointment if you have:
– Mouth sores that don’t heal in 2 weeks
– Severe pain that makes eating or drinking difficult
– Sores that keep coming back, are unusually large, or multiply
– Fever, swollen glands, or spreading redness
– Signs of dehydration (especially in kids or older adults)
For frequent cold sores, prescription antivirals can shorten and reduce outbreaks. For recurrent canker sores, your dentist can rule out irritants, discuss nutrition, and suggest targeted therapies.
Practical prevention tips (easy wins)
Cut down triggers
– Manage stress with short daily walks, breathing exercises, or stretching
– Protect lips from sun and wind with SPF lip balm (yes, even in Canadian winters)
– Keep a food diary if you suspect diet triggers (e.g., citrus, tomatoes, nuts for canker sores)
Keep your mouth comfortable
– Aim for steady hydration—dry mouth can worsen irritation; if you struggle, explore simple dry mouth remedies
– Use a soft‑bristled brush and be gentle along the gum line
– If braces or a sharp tooth edge rubs a spot, ask your dentist about smoothing or protective wax
Hygiene matters
– Don’t pick at cold sores or share lip products
– Replace your toothbrush after a cold sore crusts over, or if a canker sore was caused by trauma from frayed bristles
– Rinse after meals; gentle salt water is fine
Safe treatments (what to expect)
For canker sores
– Over‑the‑counter: benzocaine gels, barrier patches, and mild oral rinses can ease pain
– In‑office: if sores are frequent or severe, dentists may prescribe steroid gels/rinses or recommend testing for nutritional deficiencies
– Lifestyle: consider testing an SLS‑free toothpaste for a month if you notice a pattern
For cold sores
– Over‑the‑counter: docosanol at the first tingle may help shorten an outbreak
– Prescription: oral antivirals (e.g., acyclovir, valacyclovir) are used for severe or frequent outbreaks—your dentist or family doctor can advise
– Sun/wind care: SPF lip balm and a good moisturizer reduce cracking and flares
What to avoid
– Applying undiluted essential oils directly on sores (risk of burns)
– Abrasive or alcohol‑heavy rinses that sting and delay healing
– Sharing drinks, utensils, or lip balms during a cold sore outbreak
– Picking scabs or blisters—this increases the chance of spread or secondary infection
Kids, teens, and older adults
– Kids/teens: Canker sores can follow braces adjustments or sports mouth trauma. A mouthguard for hockey or basketball helps. Use orthodontic wax as needed and keep lips protected outdoors.
– Older adults: Dry mouth from medications is common and can make tissues fragile. Ask your dentist about saliva‑support strategies if you’re noticing frequent irritation, and review medications during checkups.
Bad breath with sores?
It’s common to notice a temporary odour when sores make brushing uncomfortable. Gentle, regular hygiene and rinsing after meals help. If breath issues persist after healing, see our tips to prevent bad breath.
Canada‑specific notes
– Cold weather and indoor heating can dry lips and oral tissues, increasing cracking and flare‑ups—keep a small lip balm with SPF handy, even in winter.
– For sports (hockey, ringette, basketball), a well‑fitted mouthguard reduces soft‑tissue trauma that can lead to canker sores.
Quick self‑check (what do you likely have?)
– Inside mouth, round/oval, white/yellow centre, not contagious? Likely a canker sore.
– On/around lip, tingling then blisters and crust, contagious? Likely a cold sore.
Unsure, severe, or lingering? Book a dental exam—better to be safe.
Conclusion
Canker sores and cold sores may look similar at first, but they have different causes, risks, and treatments. Canker sores form inside the mouth and aren’t contagious; cold sores are viral and spread easily, usually appearing on or near the lips. With gentle home care, targeted products, and the right prevention habits, most people feel better within 1–2 weeks. If a sore doesn’t heal, keeps coming back, or interferes with eating or drinking, your dentist can help you pinpoint triggers and build a simple plan to stop the cycle.
FAQ
1) Are canker sores contagious?
No. Canker sores (aphthous ulcers) aren’t caused by a virus and don’t spread to others. They’re often linked to irritation, stress, or food sensitivity.
2) Are cold sores contagious even without a visible blister?
Yes. HSV‑1 can shed before blisters appear and after they heal. Avoid kissing or sharing drinks when you feel a tingle or notice a sore.
3) What’s the fastest way to treat a cold sore?
Start an antiviral cream at the first tingle. For frequent or severe outbreaks, ask your dentist or family doctor about a prescription antiviral taken at the earliest sign.
4) My mouth feels dry and I’m getting more sores. What can I do?
Dry mouth irritates tissues and slows healing. Sip water regularly, consider sugar‑free xylitol gum, use gentle rinses, and review more tips in our guide to dry mouth relief.
5) How long should I wait before seeing a dentist about a sore?
If a sore hasn’t improved in 1–2 weeks, is very painful, or keeps returning, book a dental visit. Any non‑healing spot should be checked—early evaluation is best.
6) Could a non‑healing sore be oral cancer?
Most mouth sores aren’t cancer. But an ulcer or patch that doesn’t heal in two weeks needs a professional assessment. Learn more about signs and screening in our oral cancer screenings article.
