Medical Conditions



Mouth Sores

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What are the causes of mouth sores?

Herpes simplex, canker sores, hand-foot-and-mouth disease, and thrush

What is herpes simplex?

  • A virus that can cause a variety of infections in different age groups.

  • In early childhood, most commonly causes blister-like sores (vesicles) in the mouth, around the lips, and on skin that is in contact with the mouth, such as a sucked thumb or finger.

  • Virus may be shed by children and adults with no signs or symptoms.

  • Herpesviruses stay in the body without symptoms after initial infection; recurrent disease may occur because of a variety of triggers, such as stress, cold, or sunlight.

  • See Herpes Simplex (Cold Sores) Quick Reference Sheet for more details.

What are canker sores?

  • Shallow ulcers in the mouth and inside of lips and gums.

  • The cause is not known but may be related to trauma from biting the inside of the cheek or lip or from injury to mouth tissues while brushing teeth.

  • These sores are not contagious.

What is hand-foot-and-mouth disease?

  • A virus (enterovirus) that can cause a rash on the hands and feet and shallow ulcers on the inside of the mouth.

  • See Hand-Foot-and-Mouth Disease Quick Reference Sheet for more details.

What is thrush?

  • White patches on the inside of the cheeks, gums, and tongue caused by a fungus/yeast called Candida.

  • See Thrush (Candidiasis) Quick Reference Sheet for more details.

What are the signs or symptoms?

  • Herpes is the most severe of these conditions, and a primary or initial infection may result in

    • Fever.

    • Irritability.

    • Tender, swollen lymph nodes.

    • Painful, small, fluid-filled blisters (vesicles) in the mouth and on the gums and lips.

    • Vesicles weep clear fluid, bleed, and are slow to crust over.

  • Canker sores and hand-foot-and-mouth disease may cause pain with eating and swallowing. Some children will drool excessively because it hurts to swallow the saliva.

  • Thrush does not usually cause discomfort unless the infection is severe.

What are the incubation and contagious periods?

See individual Quick Reference Sheets for herpes simplex, hand-foot-and-mouth disease, and thrush. Canker sores are not known to be contagious.

How is it spread?

See individual Quick Reference Sheets for herpes simplex, hand-foot-and-mouth disease, and thrush.

How do you control it?

See individual Quick Reference Sheets for herpes simplex, hand-foot-and-mouth disease, and thrush. There is no cure for canker sores. They must run their course for 1 or 2 weeks. Pain medication, such as acetaminophen (eg, Tylenol) or ibuprofen (eg, Advil, Motrin), may be used.

What are the roles of the teacher/caregiver and the family?

  • Report these conditions to the staff member designated by the child care program or school for decision-making and action related to care of ill children. That person, in turn, alerts possibly exposed family and staff members to watch for symptoms.

  • Stress the importance of good hand hygiene and other measures aimed at controlling the transmission of infected secretions (eg, saliva, tissue fluid, fluid from a skin sore).

  • Wash and sanitize mouthed toys, bottle nipples, and utensils that have come into contact with saliva or have been touched by children who are drooling and put fingers in their mouths.

  • Avoiding touching cold sores with hands. This is difficult but should be attempted. When sores have been touched, careful hand hygiene should follow immediately.

Exclude from group setting?

No, unless

  • The child has mouth ulcers and blisters and does not have control of drooling. (Exception: For hand-foot-and-mouth disease with drooling, children do not need to be excluded for inability to control the drooling.)

  • The child is unable to participate and staff members determine they cannot care for the child without compromising their ability to care for the health and safety of the other children in the group.

  • The child meets other exclusion criteria.

Note: Children and teachers/caregivers with recurrent infection (ie, cold sores) do not need to be excluded.

Readmit to group setting?

Yes, when all the following criteria have been met:

  • When no drooling or exposed open sores

  • When the child is able to participate and staff members determine they can care for the child without compromising their ability to care for the health and safety of the other children in the group

Listing of resources does not imply an endorsement by the American Academy of Pediatrics (AAP). The AAP is not responsible for the content of external resources. Information was current at the time of publication.

The information contained in this publication should not be used as a substitute for the medical care and advice of your pediatrician. There may be variations in treatment that your pediatrician may recommend based on individual facts and circumstances.

Quick Reference Sheet from Managing Infectious Diseases in Child Care and Schools: A Quick Reference Guide.

© 2017 American Academy of Pediatrics. All rights reserved.

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