If you’ve ever had a canker sore, you know the pain — that small, angry ulcer that turns eating, brushing, and even talking into a nightmare. And if you get them often, you’ve probably found yourself Googling: Why do I keep getting canker sores? What causes them? And more importantly — how can you prevent them?
Let’s break down the most common (and some surprising) reasons for canker sores, and what you can do to get lasting relief.
What Is a Canker Sore, Exactly?
Canker sores are small, shallow lesions that form inside the mouth: on your tongue, inner cheeks, lips, or gums. They’re not contagious, unlike cold sores, and they usually heal on their own within 7–14 days.
But for frequent sufferers, canker sores can feel like a never-ending cycle. To stop that cycle, you have to understand the root causes.
1. Nutritional Deficiencies
One of the most overlooked causes of canker sores is a lack of essential vitamins and minerals. Your mouth tissue needs specific nutrients to stay strong and resilient.
Common deficiencies linked to canker sores:
- Vitamin B12
- Folate (Vitamin B9)
- Zinc
- Iron
Studies have shown that Vitamin B12 deficiency, in particular, can lead to recurring sores. One study published in the Journal of the American Board of Family Medicine found that B12 supplementation significantly reduced both the frequency and duration of canker sores over time.
If you’re vegetarian, vegan, or have absorption issues (like with Crohn’s or celiac disease), your risk is even higher.
2. Stress and Hormonal Changes
Ever noticed a canker sore pop up right before a big presentation, final exam, or family drama? That’s not a coincidence.
Emotional stress weakens your immune system and can trigger inflammation — two perfect storm ingredients for mouth ulcers.
Women may also notice canker sores cyclically, especially before their period due to hormonal fluctuations.
What you can do:
- Practice stress-reducing habits: meditation, exercise, deep breathing
- Track your outbreaks to see if they follow a hormonal pattern
- Consider adaptogens or magnesium for hormone and stress support
3. Mouth Trauma (Even Tiny Ones)
You might not even notice when it happens — but minor trauma inside your mouth is a big cause of canker sores.
Examples:
- Accidentally biting your cheek or tongue
- Brushing too hard
- Using a toothbrush with stiff bristles
- Dental appliances like braces or ill-fitting retainers
Even a rogue tortilla chip with a sharp edge can be the culprit.
If you get a canker sore in the exact same spot repeatedly, you may have a habitual biting spot or irritation from dental work — something worth bringing up with your dentist.
4. Certain Ingredients in Toothpaste and Mouthwash
This one surprises a lot of people. Some common oral care products contain sodium lauryl sulfate (SLS) — a foaming agent known to irritate mouth tissue and increase canker sore frequency.
Check your labels for:
- Sodium lauryl sulfate (SLS)
- Harsh alcohols or antiseptics
- Artificial dyes or sweeteners
Try switching to a SLS-free toothpaste and alcohol-free mouthwash for a few weeks to see if things improve.
5. Food Sensitivities
Certain foods can trigger canker sores, especially acidic or spicy foods that irritate the lining of your mouth.
Common triggers:
- Citrus fruits (oranges, lemons, grapefruits)
- Tomatoes
- Strawberries
- Pineapple
- Vinegar-based foods (pickles, dressings)
- Chocolate (sorry)
- Coffee
You might also react to gluten or dairy if you have a sensitivity or intolerance.
Try keeping a food diary to track outbreaks. If you notice a pattern, try an elimination diet or talk to a nutritionist.
6. Immune System Imbalances
Canker sores are thought to have an autoimmune component, especially when they’re frequent or severe.
Conditions like:
- Celiac disease
- Crohn’s disease
- Ulcerative colitis
- Lupus
- or Behçet’s disease
can all make you more prone to mouth ulcers. If your canker sores are frequent, large, or come with other symptoms (digestive issues, joint pain, fatigue), talk to your doctor about underlying autoimmune or GI conditions.
7. Genetics
Yes, unfortunately — sometimes it runs in the family. If one or both of your parents had frequent canker sores, you’re more likely to get them too.
This doesn’t mean you’re stuck with them forever, but it does mean you may have to be more proactive with prevention than someone who gets them occasionally.
How to Stop Getting Canker Sores: Prevention Tips That Work
Now that you know the causes, here’s what you can do to reduce how often you get them — or stop them altogether.
Daily Prevention Tips:
- Supplement with B12 and Zinc — or try a lozenge like Cankies that combines these with soothing ingredients.
- Switch your toothpaste — SLS-free is the way to go.
- Eat a nutrient-rich diet — focus on leafy greens, lean protein, and anti-inflammatory foods.
- Avoid known trigger foods — especially acidic or spicy ones.
- Use a soft-bristled toothbrush and be gentle when brushing.
- Manage your stress with movement, meditation, or therapy.
- Sleep well — your immune system heals while you rest.
What About Treatment?
Most canker sores go away on their own in a week or two, but that doesn’t mean you have to suffer. Here’s what actually helps:
- Topical numbing gels (benzocaine or lidocaine)
- Salt water rinses or baking soda rinses
- Aloe vera gel for soothing
- Vitamin lozenges with B12, lysine, zinc, or licorice root extract (like Cankies!)
- Avoid spicy/acidic foods while healing
When Should I See a Doctor?
While most canker sores are harmless, see your dentist or doctor if:
- A sore lasts more than 3 weeks
- You get multiple sores at once frequently
- Sores are unusually large or painful
- You have accompanying symptoms like fever, diarrhea, or joint pain
- You suspect an underlying health condition (GI, autoimmune, etc.)
Final Thoughts
Canker sores are frustrating — but they’re also your body’s way of signaling that something’s off. Whether it’s stress, nutrient deficiencies, or irritation from toothpaste, you can take steps to reduce how often you get them.
Want a simple, science-backed solution you can start today? Try Cankies — a lozenge made with ingredients shown to help your mouth heal from the inside out. Cankies can help heal your sores and also is safe enough for daily use to prevent you from getting canker sores in the future.
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