Merck Manual

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Some Causes of Mouth Sores

Some Causes of Mouth Sores



Bacterial infections

Fungal infections

Candidal infections (most common)

Chickenpox (varicella zoster)

Others (such as infection by coxsackievirus, cytomegalovirus, Epstein-Barr virus, or HIV, as well as genital warts, influenza, and measles)

Systemic disorders

Cyclic neutropenia

Platelet disorders

Thrombotic thrombocytopenia

Vitamin B12 deficiency




Physical irritation

Cheek-biting or lip-biting habits

Dentures that fit poorly

Jagged or broken teeth

Irritants and allergies

Acidic foods

Allergic reaction to ingredients in toothpaste, mouthwash, candy, gum, dyes, or lipstick

Aspirin, when applied to tissues inside the mouth

Dental appliances containing nickel or palladium

Occupational exposure to dyes, heavy metals, acid fumes, or metal or mineral dust

Tobacco (chewing and/or smoking)


Radiation therapy to the head and neck

* Rare causes of mouth sores.