An eruption cyst is a soft, dome-shaped bump on the gum that forms over a tooth about to come through, and when it fills with a little blood it looks blue or purple and is called an eruption haematoma. It is a harmless part of teething that most often appears over an incoming baby tooth or a child’s first adult molar. In almost all cases it needs no treatment and settles on its own as the tooth breaks through the gum.
Key takeaways
- An eruption cyst is a fluid-filled bump over an erupting tooth; when blood-tinged it is an eruption haematoma and looks blue or purple.
- It is a normal, harmless part of teething and usually needs no treatment.
- Do not try to pop or drain it, as this can introduce infection.
- See a dentist if it lasts more than a couple of weeks, looks infected, or the child is in significant pain.
What an eruption cyst is
As a tooth moves up through the jaw, it has to pass through the gum. Sometimes a small sac of fluid collects in the gum tissue just above the crown of the incoming tooth, forming a soft, raised bump. If the fluid is clear the bump can look translucent or bluish-white; if a little blood mixes in, it takes on a blue or deep purple colour and is called an eruption haematoma. The colour can look alarming to a parent, but the bump is simply the gum stretched over a tooth that is on its way, and it is not a bruise or an injury.
Where and when they appear
Eruption cysts appear at the ages when teeth are coming through. In babies and toddlers they show up over erupting baby teeth, often the front teeth or first molars. In children around the age of six, they can appear over the first permanent molars at the back of the mouth. They tend to come and go with the teething process, and a child may have more than one over the years. Mild tenderness in the area is common, much like ordinary teething. Our guide on natal and neonatal teeth covers another early-tooth situation parents sometimes meet.
Why not to pop it
It is natural to want to help the tooth through, but an eruption cyst should be left alone. The gum over it is a natural barrier, and trying to pierce, squeeze or drain the bump breaks that barrier and can let bacteria in, risking an infection that is far more troublesome than the harmless cyst. In the great majority of cases the tooth simply erupts through the bump over days to weeks, the fluid or blood drains away naturally, and the gum settles. Cold, safe teething comforters can ease any discomfort while nature takes its course. The table below summarises the sensible approach.
| Situation | What to do |
|---|---|
| Soft bluish bump, child comfortable | Leave it alone and let the tooth come through |
| Mild teething discomfort | A chilled teething ring and usual teething comfort measures |
| Bump lasting more than a couple of weeks | Have a dentist take a look |
| Redness, pus, swelling or significant pain | See a dentist, as this suggests infection |
When to see a dentist
Most eruption cysts never need a visit, but it is worth having one checked if it lasts more than a couple of weeks without the tooth appearing, if it looks infected with redness, pus or spreading swelling, or if your child seems to be in more than mild discomfort. Very occasionally, if a tooth is slow to break through, a dentist can make a tiny opening in the gum to uncover the tooth, but this is rarely needed. A dentist can also confirm that a bump is an eruption cyst rather than something else. Our note on a gum boil explains a different kind of gum bump, one linked to infection, so you can tell them apart.
Reassurance for parents
An eruption cyst is one of those things that looks worse than it is. A blue bump on a baby’s gum understandably worries parents, but it is a normal sign that a tooth is on its way and it almost always resolves by itself. Keep up gentle mouth care, wiping the gums or brushing softly as usual, offer safe teething comfort, and let the tooth do the work. If anything about it seems off, a quick check with a dentist provides peace of mind. This is general information and not a diagnosis of your child’s situation.
Frequently asked questions
Is a blue bump on my baby’s gum dangerous?
Almost never. A soft blue or purple bump over an incoming tooth is usually an eruption haematoma, a harmless part of teething that settles as the tooth comes through.
Should I pop the eruption cyst?
No. Popping or draining it can introduce infection. The gum over it is a natural barrier, and the tooth will come through on its own.
How long does an eruption cyst last?
Usually days to a couple of weeks, resolving as the tooth erupts. If it lingers beyond that without the tooth appearing, have it checked.
How is it different from a gum boil?
An eruption cyst sits over an incoming tooth and is part of teething. A gum boil is a pimple-like bump linked to infection and usually needs dental treatment.
Can I do anything to help?
Offer safe, chilled teething comforters for discomfort and keep up gentle mouth cleaning. Otherwise, let the tooth come through naturally and see a dentist if you are concerned.
If your child has a gum bump you are unsure about, the team at Lumi Dental in Melrose Park is happy to take a look and reassure you. Learn about our general dental care or see our current deals. We do not publish prices in our articles and are happy to provide a written estimate after an examination.
This article is general information only and is not a substitute for personalised dental advice. Please see a dentist about your child’s situation.
