Canker sores — also known as aphthous ulcers — are small, shallow ulcers that form inside the mouth. They often appear as white or yellow spots with a red border. While they’re usually tiny (less than 1 millimeter), some can grow up to half an inch or even an inch in diameter.
You can get canker sores on your tongue, gums, the roof of your mouth, inside your lips, or under your tongue. They can be quite painful and make eating, drinking, and talking uncomfortable.
Types of Canker Sores
There are two main types:
- Simple canker sores: These are the most common, usually appearing a few times a year and healing in about a week.
- Complex canker sores: Less common but often recurring, especially in people with a history of frequent canker sores.
Are Canker Sores an STI?
No. Canker sores are not herpes or any other sexually transmitted infection (STI). They are not contagious and cannot spread through kissing or sexual contact.
Canker Sores vs. Cold Sores: What’s the Difference?
Canker sores and cold sores are often confused, but they are very different:
- Cold sores (also called fever blisters) are caused by the herpes simplex virus (HSV-1 or HSV-2). They are contagious, fluid-filled blisters that often form around the lips or genitals and spread through close personal contact.
- Canker sores are not caused by an infection, are not contagious, and only occur inside the mouth.
Who Gets Canker Sores?
Anyone can develop them, but they are more common in:
- Teens and young adults in their 20s
- Women, possibly due to hormonal changes
How common are they? Canker sores are very common, affecting about 20% of people in the U.S. at some point in their lives.
Symptoms of Canker Sores
Typical signs include:
- One or more painful sores inside the mouth (on the tongue, lips, cheeks, or palate)
- A burning or tingling sensation before the sore appears
- Round or oval ulcers that are white, gray, or yellow with a red border
In severe cases, you might also experience:
- Fever
- Fatigue or sluggishness
- Swollen lymph nodes
What Causes Canker Sores?
The exact cause isn’t always clear, but common triggers include:
- Stress or fatigue
- Minor mouth injuries (biting your cheek, irritation from braces, etc.)
- Acidic or spicy foods (like citrus or tomatoes)
- Certain medications (NSAIDs like ibuprofen)
- Ill-fitting dentures or dental appliances
Underlying health conditions
Complex canker sores are sometimes linked to:
- Autoimmune diseases (Lupus, Behcet’s disease)
- Celiac disease
- Ulcerative colitis or Crohn’s disease
- AIDS or immune system disorders
Nutritional deficiencies
Low levels of vitamin B12, folic acid, zinc, or iron may also increase the risk.
While canker sores are usually harmless and heal on their own, recurring or severe sores can make eating, speaking, and daily life uncomfortable. They may also be a sign of an underlying condition or nutritional deficiency that needs attention.
If you experience frequent mouth ulcers or have one that doesn’t heal within two weeks, don’t ignore it. A professional dental exam can help determine the cause and provide relief quickly.***