Cold Sores vs. Afters: How to Know the Difference

Cold Sores vs. Afters: How to Know the Difference

Many Danes confuse cold sores with canker sores – two common but different mouth conditions. While both can be painful and annoying, they have different causes and require different treatments. In this blog post, we explain how you can easily tell the difference – and when you should seek help.

 

What is a cold sore?

Cold sores are caused by a viral infection – herpes simplex virus type 1 (HSV-1). They often start with a tingling or burning sensation on the lip, followed by small fluid-filled blisters that burst and form sores. These are highly contagious, especially before and during the outbreak.

Cold sores typically occur on the outside of the mouth, around the lips or on the nose. However, they can also occur inside the mouth, but only on the hard palate or gums – never on soft tissues such as the inside of the cheeks or the tongue.
• Risk of infection: Very high – spread via kissing, sharing glasses/cutlery, etc.
• Appearance: Clear blisters that burst and turn into ulcers with crusts.
• Duration: 7–14 days.
• Cause: HSV-1 virus.

What is after?

Canker sores (also called aphthous ulcers) are small, round or oval white sores that appear inside the mouth – typically on the inside of the cheek, tongue, inside of the lip or soft palate. They are not contagious and are not caused by a virus, but are often caused by irritation, vitamin deficiency, hormonal changes or stress.

Cold sores are very common and often occur spontaneously. They start as a slight tingling or soreness and quickly develop into a small sore surrounded by a red ring.
• Risk of infection: None – not caused by virus.
• Appearance: White/yellow center with red edge, smooth surface.
• Duration: 5–10 days.
• Cause: Unknown – but related to irritation, stress, foods or immune system.

How do you know the difference?

Property	Cold sores	After
Location	Cleft lip or hard palate	Inside the mouth, on the tongue or cheek
Appearance	Blisters → sores with crusts	White sore with red ring, no crust
Risk of infection	Yes (HSV-1 virus)	No
Cause	Virus (herpes simplex)	Unknown – non-virus
Duration	7–14 days	5–10 days
Treatment	Cream/gel against herpes.	Local anesthesia, bland diet, relief

When should you seek help?

• If you get frequent cold sores (more than 6 times a year), preventive antiviral treatment may be considered.
• If you have many or very painful after-effects, you should be examined for vitamin deficiencies (B12, iron, folic acid) or gastrointestinal problems such as celiac disease.
• If you have a fever, swollen lymph nodes or if the wounds do not heal, you should contact a doctor.

Conclusion

Although cold sores and canker sores can be confused, there are distinct differences in cause, location, and appearance. Knowing these differences can help you choose the right treatment more quickly—and in some cases, avoid infecting others.