Swollen gums in a child can look alarming, but the cause and urgency vary considerably. Some causes are completely benign and will resolve on their own. Others need to be seen promptly. Here is how to read the signs.
Teething
In babies and toddlers, the most common cause of swollen or tender gums is a tooth erupting through the gum. As the tooth pushes upward, the gum tissue over it stretches and can appear puffy, red or bruised. This is normal.
Teething swelling is typically localised to the area where a tooth is coming in, comes and goes, and follows the normal eruption sequence. The child may drool, chew and be irritable for a few days, but should not have a high fever.
A blue or dark bruise-like lump over an erupting tooth is called an eruption cyst or eruption haematoma. It looks dramatic but almost always resolves on its own as the tooth breaks through. No treatment is usually needed, but it is worth showing to the dentist at the next visit.
Gingivitis — gum inflammation from plaque
The most common gum problem in older children is gingivitis — inflammation of the gum caused by plaque (the soft bacterial film that builds up on teeth). Signs include: gums that are red or swollen along the gum line, gums that bleed when brushing, and bad breath.
Gingivitis is reversible with improved brushing and flossing. The American Academy of Pediatric Dentistry (AAPD) notes that gingivitis is nearly universal in children to some degree, particularly during the mixed dentition phase when teeth are at different heights and plaque is harder to remove.
If bleeding and swelling persist despite good brushing for two weeks, book an appointment for a professional clean and assessment.
Dental abscess — act the same day
A dental abscess is a collection of pus caused by a bacterial infection — usually stemming from an untreated cavity that has reached the pulp of the tooth. An abscess causes: a localised swelling of the gum that may look like a pimple or blister (a "gum boil"), pain when biting or pressure on the tooth, sometimes swelling of the face or jaw, and occasionally fever.
A swollen face alongside tooth or gum pain means same-day contact. Dental infections can, in rare cases, spread to surrounding spaces. Do not apply heat to a swollen face — it can encourage the infection to spread.
Pericoronitis — swelling around an erupting molar
When a molar (particularly a first permanent molar, around age 6–7) is partially erupted, the flap of gum tissue over it can become inflamed — a condition called pericoronitis. Food and bacteria get trapped under the flap. Signs include swelling at the back of the mouth on one side, pain when biting and sometimes a bad taste. It usually settles with gentle cleaning of the area and, if needed, treatment.
When to contact us
Contact us the same day if: the gum or face is visibly swollen and the swelling is spreading; your child has a fever alongside gum swelling; your child cannot open their mouth fully or is having difficulty swallowing; there is pus or discharge from the gum.
Book a routine appointment if: gums bleed regularly when brushing and do not improve with better hygiene; you notice a persistent pimple on the gum that does not resolve; swelling recurs in the same spot.
Sources: American Academy of Pediatric Dentistry, Guideline on Periodicity of Examination, Preventive Dental Services, Anticipatory Guidance/Counseling, and Oral Treatment for Infants, Children and Adolescents, 2022; American Academy of Pediatric Dentistry, Policy on Early Childhood Caries (ECC), 2023.