020 3745 7455 | Book Online

What are Mouth Sores?

Mouth sores are painful lesions that can develop on the inside of the mouth, including the lips, cheeks, tongue, and gums. These sores can be bothersome, causing discomfort, pain, and difficulty eating or speaking. There are several types of mouth sores, each with its own distinct causes and characteristics.

Types of Mouth Sores:

  • Mouth ulcers: aphthous ulcers  are shallow, round, or oval sores with a white or yellowish centre and a red border. They can develop singly or in clusters and are not contagious. The exact cause of canker sores is unknown, but factors such as stress, certain foods, minor injuries to the mouth, and hormonal changes may contribute to their occurrence.
  • Cold Sores: Cold sores, also called fever blisters, are caused by the herpes simplex virus (HSV-1). They typically appear as clusters of small, fluid-filled blisters that often break open and form a crust. Cold sores are contagious and can be spread through close contact, such as kissing or sharing utensils or towels.
  • Oral Thrush: Oral thrush is a fungal infection caused by the overgrowth of Candida fungus in the mouth. It appears as creamy white lesions on the tongue, inner cheeks, or roof of the mouth. Oral thrush is more common in individuals with weakened immune systems, those taking antibiotics, or those with conditions that affect the balance of microorganisms in the mouth.

Symptoms of Mouth Sores:

Mouth sores can cause various symptoms, including:

  • Pain or discomfort: Mouth sores can be painful, making it uncomfortable to eat, drink, or speak.
  • Sensitivity: Sores in the mouth can make the affected area sensitive to touch, heat, or cold.
  • Redness and inflammation: The surrounding area of the sore may appear red and inflamed.
  • Difficulty in eating and drinking: Depending on the location and size of the sores, they can make it challenging to chew, swallow, or consume certain foods and beverages.
  • Burning or tingling sensation: Some individuals may experience a burning or tingling sensation before the sores become visible.

Speak to a dental professional today

Our dentists have all the experience, skill and technology required to advice on mouth sores. Arrange an appointment with our dental team at our central London dental clinic, situated on the prestigious Wimpole Street.

Common Causes of Mouth Sores:

The causes of mouth sores can vary depending on the type of sore:

  • Mouth ulcers: While the exact cause is unknown, potential triggers for mouth ulcers include stress, injury to the mouth (such as biting the inside of the cheek), certain foods or food sensitivities (such as citrus fruits or spicy foods), hormonal changes, and underlying health conditions.
  • Cold Sores: Cold sores are caused by the herpes simplex virus type 1 (HSV-1). The virus is highly contagious and can be transmitted through direct contact with an active sore or the fluid from the blister.
  • Oral Thrush: Oral thrush is caused by an overgrowth of the Candida fungus, which is normally present in the mouth in lesser amounts. Certain factors can contribute to the development of oral thrush, such as weakened immune system, use of antibiotics or corticosteroids, diabetes, or wearing dentures that don’t fit properly.

How do you treat Mouth Sores?

The treatment of mouth sores depends on the underlying cause:
Mouth ulcers: Most heal on their own within one to two weeks without specific treatment. Over-the-counter topical gels or ointments containing benzocaine or numbing agents can help alleviate pain. In severe cases, a healthcare professional may prescribe stronger medications or recommend oral rinses to reduce inflammation and promote healing.
Cold Sores: Cold sores caused by the herpes simplex virus cannot be cured, but antiviral medications can help reduce the severity and duration of outbreaks. These medications are most effective when taken at the first sign of a cold sore. Applying over-the-counter creams or ointments may help relieve symptoms and promote healing.
Oral Thrush: Treatment for oral thrush usually involves antifungal medications, such as oral rinses or lozenges, which are prescribed by a healthcare professional. Good oral hygiene practices, such as regular brushing and flossing, along with removing and cleaning dentures, can help prevent oral thrush.


In addition to specific treatments for each type of mouth sore, there are general measures that can help alleviate discomfort and promote healing. These include avoiding spicy or acidic foods, practicing good oral hygiene, using a soft-bristled toothbrush, avoiding irritants such as tobacco and alcohol, and managing stress levels.


If you have recurring or persistent mouth sores, it is recommended to consult a healthcare professional for an accurate diagnosis and appropriate treatment.


In conclusion, mouth sores can cause discomfort and difficulty in daily activities. mouth ulcers, cold sores, and oral thrush are common types of mouth sores, each with its own causes and characteristics. Treatment options vary depending on the type of sore and can include topical ointments, antiviral medications, antifungal treatments, and supportive care measures. Seeking professional medical advice is important for accurate diagnosis and appropriate management of mouth sores.

Prof Christian Mehl

Written by: Prof Dr Christian Mehl

A certified implantologist and prosthodontics specialist with 20+ years in dentistry, I conduct clinical research, teach at University of Kiel, and contribute to implant system development. Recipient of the Camlog Research Award, I frequently publish and deliver global lectures.

Clinically reviewed by: Dr Raul Costa

When did we last update this page?

Our expert team continually update and research the latest news and techniques in dentistry, as such we regularly update our pages and have these clinically reviewed.

Current Version

July 21st 2023

  • Added “when did we last update this page” and author biography to the page.

Written by: Prof Dr Christian Mehl

Medically reviewed by: Dr Raul Costa

Previous Versions

October 2nd 2022

  • Page redesigned and updated to reflect change in address.

Written by: Prof Dr Christian Mehl

Medically reviewed by: Dr Raul Costa

30th August 2021

  • Original content created.

Written by: Prof Dr Christian Mehl

Medically reviewed by: Dr Raul Costa

Wimpole St Dental Clinic has strict sourcing guidelines and relies on peer-reviewed studies, academic research institutions, and medical associations. We avoid using tertiary references. You can learn more about how we ensure our content is accurate and current by reading our editorial policy.