Eruption Cyst: Purple or Blue Bump on a Baby's Gums

A purple, blue or bluish-black bump on your baby’s gum, right over a tooth that’s coming in, is usually an eruption cyst. It’s a harmless bubble of fluid that goes away on its own once the tooth breaks through.

A dark bump looks alarming. In an eruption cyst, the color comes from a little blood in the fluid and isn’t a sign of trouble. Have your child’s dentist check it to confirm that’s what it is.

Call your child’s dentist if the bump isn’t gone after two weeks, if it seems infected, or if your child seems to have pain when eating. Kids older than babies can get them too, especially with their permanent molars.

What Is an Eruption Cyst on a Baby’s Gums?

An eruption cyst is a soft, fluid-filled bump in the gum that’s covering a tooth that’s coming in. When a baby tooth or permanent tooth starts to come in, sometimes fluid collects in the sac around the top of the tooth.

That can make the gum over the sac swell into a little dome just before the tooth comes in. It goes away once the tooth erupts.

Eruption Cyst vs. Eruption Hematoma

When there’s blood in the sac, it’s sometimes called an eruption hematoma. (Hematoma is the medical term for trapped blood.)

The blood makes it look dark blue, purple, or nearly black. Think “black and blue.” A hematoma is treated the same way as a clear or blue eruption cyst, and the dark color alone doesn’t mean something is wrong.

Symptoms of an Eruption Cyst

The bump itself is usually the only symptom. Your baby will probably act normally.

What Does an Eruption Cyst Look Like?

Signs of an eruption cyst:

• It has a rounded shape and feels soft, and it may look clear.
• It may have a bluish, purplish, or reddish-brown color, or look almost black if it’s filled with blood.
• It’s in the spot where a tooth is coming in, on the top or bottom gum.

Photos of eruption cysts in a baby and school-age kids, on baby and permanent teeth, are hidden below.

Pain and Other Symptoms

Most eruption cysts don’t cause pain. Some babies are fussier, drool more, or don’t want to feed or chew on that side. That’s more common with a cyst over a molar.

Worsening pain, pus draining from the bump, fever, or swelling beyond the bump are not signs of a normal eruption cyst.

Do Babies’ Gums Turn Purple When Teething?

Teething itself doesn’t turn the gums purple. Normal teething symptoms are swollen, tender gums, plus more drooling, chewing, and fussiness.

But if you see a raised, purple, blue, or blackish dome in your baby’s gum, it’s most likely an eruption cyst or hematoma. Eruption cysts happen during teething because they’re related to a tooth that’s coming in.

Extra drooling can cause a teething rash, but that’s on your baby’s skin, not the gums.

What to Do If You See One

You can’t prevent an eruption cyst, but a few steps can help your baby stay comfortable and lower the chance of the cyst getting infected:

• Leave it alone: don’t poke, squeeze or try to pop it, because that can introduce bacteria and lead to an infection.
• Keep the area clean: wipe your baby’s gums with a clean, damp cloth after feedings and brush any teeth with a soft baby toothbrush.
• Soothe sore gums: try a clean, chilled (not frozen) teething ring or cool, damp washcloth. Skip numbing gels and teething necklaces.
• Take a photo every few days: you can see if the bump is getting smaller.

How Long Does an Eruption Cyst Last?

Most eruption cysts go away on their own, but it can take weeks or sometimes months. The cyst flattens out or pops once the tooth comes in.

Call the dentist if it’s still there after two weeks.¹ That doesn’t mean it needs surgery.

What Causes an Eruption Cyst?

Eruption cysts are caused by the arrival of a tooth. Fluid pools in a sac of tissue over the tooth before it emerges from the gum. There are two sets of teeth, so you can see these at two different times.

Babies Cutting Their First Teeth

Baby teeth begin arriving at around 6 months, and continue to come in until your child is about 3 years old.⁴ In one study of 66 eruption cysts, they were most common over the upper first baby molars.

You can see them on the upper or lower gum, though. The location doesn’t mean the cyst is more or less serious.

Older Kids Getting Permanent Teeth

The first permanent teeth to come in are the 6-year molars and the front teeth (ages 6 to 8), followed by the 12-year molars (ages 11 to 13). Eruption cysts over permanent teeth look and act the same. Most of the photos here are of school-age children.

Occasionally, you may see eruption cysts in newborns, over teeth present at birth or those that come in the first few weeks.

Eruption Cyst Treatment

Most eruption cysts require no treatment. As the tooth continues to push its way up, it breaks through the dome. The swelling goes down on its own.

In one study of 53 children with 66 eruption cysts, only 7 of the children had surgery. For the rest, the dentist waited for the tooth to appear.⁵

When a Dentist Treats It

Your child’s dentist may recommend a procedure to open the cyst if:

• It lasts more than about a month
• It is painful
• It is bleeding
• It appears infected
• It interferes with eating

In this procedure, the dentist opens the top of the cyst. This allows the fluid to drain out and exposes the underlying tooth.

Your child will usually receive numbing medicine. Depending on your child, the dentist may also recommend sedation. Most children recover quickly.

If the cyst appears infected, the dentist will examine your child and recommend treatment.

Eruption Cysts vs. Other Gum Bumps

Other bumps in your child’s mouth may look similar but need different treatment:

• Mucocele: a painless, bluish or clear bump caused by saliva leaking from an injured duct, usually on the inside of the lip or cheek.
• Gum boil: a yellow or white bump filled with pus. It occurs next to a tooth that has already erupted, and is due to infection. It needs an urgent visit to the dentist, even if it doesn’t hurt.
• Bruise from a fall: if your child has fallen or bumped their mouth, the blue or purple bump may be a bruise. Take them to the dentist the same day to make sure nothing is wrong with their teeth or gums.
• Mouth sores: ulcers or blisters, which may appear with or without a fever. They can be caused by infections such as hand, foot and mouth disease, or by an injury or irritation.
• Dentigerous cyst: these form in the jawbone, around a tooth that hasn’t come in. The dentist finds them on x-rays. Eruption cysts are considered the soft-tissue form of this cyst.

When to See a Dentist or Doctor

Most eruption cysts need nothing but time. Call your child’s dentist when the bump doesn’t behave like one, and call your pediatrician when your child seems sick.

Call Your Child’s Dentist If

• The bump is still there after two weeks, or the tooth doesn’t seem to be coming through
• It keeps getting bigger, feels firm, or isn’t over a spot where a tooth is coming in
• It leaks pus or blood, or the gum turns red and swollen
• Your child seems to be in pain or won’t eat or drink because of it
• The bump or mark showed up after your child fell or took a blow to the mouth

Call Your Pediatrician the Same Day If

• Your child has a fever along with the bump
• Your baby refuses feeds or drinks much less than usual

Call your pediatrician right away for a fever of 100.4°F (38°C) or higher in a baby 3 months or younger, even if they seem well. A rectal reading is most accurate at this age, but don’t delay calling to take one. Also call right away if your baby has fewer wet diapers, a sign of dehydration.

If swelling spreads into the cheek or jaw, call your child’s dentist or doctor right away. If it spreads fast, toward or around the eye or into the neck, or your child has trouble opening their mouth, go to the emergency room. Eye pain or vision changes also need the emergency room.

Go to the emergency room for any trouble breathing or swallowing, even without facial swelling. Call 911 if your child is struggling to breathe, can’t swallow their saliva or is hard to wake.

The American Academy of Pediatric Dentistry recommends a first dental visit by your child’s first birthday or within six months of the first tooth coming in.⁸ If your baby hasn’t had one yet, an eruption cyst is a good reason to book it.