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Why Canker Sores Hurt So Much (and What To Do About It)

why do canker sores hurt


Canker sores hurt! These pesky mouth ulcers arise when you least expect them and make eating and drinking difficult for days, if not weeks. 

Fortunately, you can effectively manage canker sores — and possibly even prevent them — once you understand the cause of canker sore pain and the best methods to avoid lasting discomfort. 

What Are Canker Sores?

Canker sores, or aphthous ulcers, are shallow white lesions with inflamed pink borders that develop inside the lips and mouth. The sores are typically 1-4 mm in size, but aggressive sores can be larger than 5 mm. 

Though they’re often confused with cold sores, canker sores are not contagious or caused by the herpes virus. They’re caused by unrelated triggers. Raw canker sores are frustrating because they can make it challenging to eat, drink and even speak.


An Overview of Pain

Pain is a concept we all understand, even if we can’t define it. The medical definition of pain is an unpleasant sensation that can range from mild, localized discomfort to agony. Stimulated nerves cause the physical sensation of pain, primarily to let us know that something is wrong in our body.

We use various words to describe pain, that include stabbing, throbbing, aching, pinching and pounding. Sometimes it’s merely a nuisance, but sometimes pain is debilitating. 

Doctors categorize pain as acute or chronic. Acute pain occurs quickly with distinctive symptoms, while chronic pain is present for long periods of time, often as the result of an underlying disease or condition. 

Why Do Canker Sores Hurt?

Canker sores are relatively small, so it’s surprising they cause so much pain. It can make you wonder, why do canker sores hurt at all?

A canker sore is essentially an injury to the tissue inside your mouth. The digestive enzymes and acids in your mouth then constantly flow over this open wound, causing the pain you feel. It’s similar to spilling salt into a paper cut, but over and over. 

Triggers That Make Canker Sore Pain Worse

Though canker sore pain seems fairly constant, certain factors can exacerbate your discomfort. Avoid the following triggers to prevent further pain in your mouth. 

Injury in the Mouth

Injury and irritation to your cheeks, gums, or tongue can irritate existing canker sores, or even cause new canker sores to develop. This is especially true for people with braces or dental appliances that rub against the inside of the mouth. Other causes of oral injury include:

  • Vigorous brushing
  • Excessive flossing
  • Using toothpicks
  • Biting your lip

Do your best to avoid these triggers by brushing gently and cleaning your dental appliances daily. You can also purchase dental wax to place a soft buffer between your braces and any canker sores. 

Allergy to Oral Care Products

Toothpaste and mouthwash products containing sodium lauryl sulfate (SLS) are especially notorious for irritating the mouth. SLS functions as a “surfactant” that produces cleansing and foaming action. Though the FDA claims SLS is safe, thousands of studies have explored the toxicity of SLS and associate the ingredient with skin irritation and organ system toxicity.

Acidic, Salty or Spicy Foods

Acidic fruits and vegetables, such as lemons, pineapples, tomatoes and oranges, can irritate canker sores and worsen pain. Excessively salty or spicy foods may also further irritate canker sores.

why do canker sores hurt


How Long Does Canker Sore Pain Last?

Once your canker sore heals, you should no longer experience any canker sore pain. It’s hard to predict how long a canker sore will linger in your mouth. Depending on the type of canker sore you have and whether you take care of it, your mouth ulcer may last days or weeks. 


Minor canker sores are the most common, accounting for about 80% of canker sore cases. These are small sores that cause some discomfort but no scarring. In most cases, minor canker sores heal within a week. 


Major canker sores, on the other hand, are less common and cause more severe side effects. These sores can last more than two weeks and grow to over 1 centimeter in diameter. Patients usually experience extreme pain and discomfort during major canker sore outbreaks. 


Herpetiform canker sores only occur in about 5% of people with canker sores. Small ulcers cluster together to form a much larger ulcer, but these tend to heal within a week. 


Complex canker sores spread to 5 mm or more and linger weeks longer than the standard ulcers. Instead of healing on their own over the span of one or two weeks, complex canker sores continue to create pain and discomfort in your mouth for up to six weeks at a time.


Methods To Reduce Canker Sore Pain

Canker sore pain is difficult to escape or ignore. Even if you can’t control how long your canker sores linger, several remedies can help you manage the pain they cause each day. 

Antimicrobial Rinse

Your dentist or doctor may recommend an antimicrobial rinse if you’re susceptible to canker sores. Listerine, Peridex and Periogard are all popular options.

These rinses may help to reduce canker sore pain and even prevent sores from developing in the future. The deep cleaning effect of antimicrobial rinses controls bacteria and plaque, which may prevent canker sores from becoming aggravated. 

Natural Remedies

Milk of magnesia, best known by the brand name Maalox®, can be blended with Benadryl® or another antihistamine to alleviate the pain caused by your canker sore. Milk of magnesia is an antacid that coats your canker sore to prevent irritation, while antihistamines treat inflammation and create a sedative effect. 

Topical Analgesics

Over-the-counter topical anesthetics like benzocaine (Kank-A) and Orajel provide safe, temporary numbing of painful sores. You can apply local anesthetics a few times a day to relieve discomfort until your canker sore heals completely. 

The Best Ways To Prevent Canker Sores

While treating canker sore pain is helpful, preventing canker sores from forming in the first place would be ideal. You may be able to prevent canker sores by boosting your body’s defenses with the following measures. 

Manage Stress

Stress is a known trigger for canker sores. Stress takes a toll on the body and may also lead to damaging behaviors known to cause canker sores, such as biting your lips and cheeks or eating problem foods.

Since you can’t eliminate stress from your life entirely, it’s important to find ways to effectively manage your stress. To begin with, make sure you eat well, get plenty of sleep and avoid excess alcohol. Beyond this, certain stress management techniques can help you cope with ongoing stress and anxiety:

  • Mindfulness breathing
  • Changing your surroundings
  • Helping others
  • Delegating small tasks to others
  • Talking to a professional

Choose Your Foods Carefully

Do your best to stay away from known canker sore trigger foods, especially if you identify one that irritates your mouth. Keeping a food journal can help you identify correlations between certain foods and the emergence of canker sores. These acidic foods are the most common culprits:

  • Oranges
  • Lemons
  • Tomatoes
  • Pineapples
  • Gluten (if you have a gluten intolerance)

Use the Luminance RED

The Luminance RED is an FDA-registered device that uses high-powered light treatment to gently alleviate painful canker sores and accelerate the healing process. Medically-optimized red light is metabolized by the skin and converted into cellular energy to accelerate healing and reduce canker sore pain.

This cutting-edge treatment has been shown to improve regular canker sores and prevent future breakouts. Data shows that when specific wavelengths of high-powered light are applied to canker sores, the average healing time falls from 8.9 days to 3.1 days. It also indicates an immediate, 92% reduction in canker sore pain.

Formerly, light therapy was only accessible in clinical settings, but today the Luminance RED is readily available and easy to use on your canker sores at home.

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