Bacterial infections

Gonorrhea

Syphilis

Trench mouth (acute necrotizing ulcerative gingivitis)

Fungal infections

Candidal infections (most common)

Viral infections

Chickenpox (varicella zoster)

Herpes simplex infection (primary or secondary)

Shingles (reactivation of varicella zoster)*

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

Systemic disorders

Behçet disease

Bullous pemphigoid or pemphigus vulgaris

Celiac disease

Cyclic neutropenia*

Erythema multiforme

Folate deficiency

Inflammatory bowel disease

Iron deficiency

Kawasaki disease

Leukemia

Platelet disorders

Stevens-Johnson syndrome

Thrombotic thrombocytopenia purpura*

(pellagra)

Vitamin B6 deficiency

Vitamin C deficiency (scurvy)

Vitamin B12 deficiency

Medications

Antibiotics*

Antiseizure medications*

Barbiturates*

Chemotherapy drugs

Gold*

Iodides*

Nonsteroidal anti-inflammatory drugs (NSAIDs)*

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

Dental appliances containing nickel or palladium

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

Tobacco (chewing and/or smoking)

Other

Burning mouth syndrome

Canker sores (recurrent aphthous stomatitis)

Lichen planus

Radiation therapy to the head and neck