An eruption cyst looks like a small, dome-shaped bump on the gum directly over a tooth that is about to come in. It is typically translucent or bluish in color, soft to the touch, and filled with clear fluid. If the fluid inside contains blood, the bump turns a deeper purple or dark blue, which is sometimes called an eruption hematoma. These cysts are most common in young children and infants during teething, though they can also appear when permanent teeth erupt.
Color, Shape, and Size
The classic eruption cyst is a well-defined, rounded swelling sitting right on the ridge of the gum where a tooth is pushing through. Because the cyst is filled with fluid, it often looks somewhat see-through or has a faint bluish tint when you pull the lip back to look at it. The surface of the gum over the cyst may appear stretched and shiny.
Color is the most variable feature. A cyst filled with clear fluid tends to look translucent or slightly pink, blending in with the surrounding gum tissue. When blood mixes into the fluid, the color shifts to a noticeable blue, purple, or even dark maroon. This blood-filled version is technically called an eruption hematoma, but it is the same type of cyst. The color difference simply reflects what is inside the fluid pocket, not a different condition or a sign of infection.
Most eruption cysts are roughly the width of the tooth crown underneath them, so they can range from a few millimeters across for a baby incisor to over a centimeter for a molar. They feel soft and squishy (clinically described as “fluctuant”), which helps distinguish them from harder lumps that might signal something else entirely.
Where They Usually Appear
Eruption cysts show up wherever a tooth is actively trying to break through the gum. In infants and toddlers, they most often appear over the front teeth or first molars during primary teething. In older children, they can develop over permanent teeth, particularly the first molars and incisors that come in around age six or seven. They occur on both the upper and lower jaws, and occasionally a child will develop more than one at the same time if multiple teeth are erupting close together.
What Causes Them
As a tooth moves upward through the jawbone and into the gum tissue, it is surrounded by a thin sac called the dental follicle. Normally, the tooth pushes straight through the gum and the follicle breaks down on its own. In some cases, fluid accumulates between the follicle and the crown of the tooth before it breaks the surface, creating a small cyst in the soft tissue. An eruption cyst is essentially the soft-tissue version of a dentigerous cyst, which forms deeper in the bone around an unerupted tooth.
The exact reason some children develop these cysts while most do not is not fully understood. Proposed triggers include minor trauma to the gums (from chewing on hard objects, for example), crowding that slows a tooth’s path, early cavities in the area, localized infection, and possibly a genetic tendency. None of these explanations account for every case, and many eruption cysts appear in perfectly healthy gums with no obvious cause.
How They Feel to Your Child
Most eruption cysts cause little or no pain. Your child might be fussy from normal teething discomfort, but the cyst itself is usually not tender unless it becomes irritated or infected. Some children are completely unbothered by it. You may notice your child drooling more than usual or chewing on things, which is standard teething behavior rather than a response to the cyst specifically.
If the bump becomes red, warm, swollen beyond the normal dome shape, or starts oozing pus, that suggests infection, which is uncommon but worth having evaluated promptly.
How Eruption Cysts Resolve
The majority of eruption cysts disappear on their own. As the tooth continues to push upward, it eventually punctures through the cyst and the gum tissue, and the fluid drains naturally. This process typically takes days to a couple of weeks. The American Academy of Pediatric Dentistry notes that because the tooth erupts through the lesion, no treatment is necessary in most cases.
If a cyst persists for several weeks without the tooth breaking through, or if it becomes infected, a dentist can perform a simple procedure to open the top of the cyst (sometimes called “unroofing”). This involves making a small incision in the gum tissue to release the fluid and expose the tooth underneath so it can continue erupting normally. The procedure is quick, and the area heals within a few days.
How to Tell It Apart From Other Gum Bumps
A few other conditions can look similar at first glance. A Bohn’s nodule or Epstein pearl, common in newborns, appears as a small white or yellowish bump on the gums or palate, but these show up in the first weeks of life before any teeth are close to erupting. A gum abscess from infection tends to be red, painful, and may produce pus, whereas an eruption cyst is typically painless and blue or translucent.
Eruption cysts are diagnosed clinically based on their appearance and location over an erupting tooth. A dentist may take an X-ray to confirm that a tooth is present underneath the bump and to rule out a dentigerous cyst, which sits deeper in the bone and can delay eruption more significantly. On an X-ray, a dentigerous cyst appears as a well-defined dark area around the crown of an unerupted tooth at the junction where enamel meets the root. An eruption cyst, by contrast, sits entirely within the soft tissue of the gum and may not show any bony changes at all.
If you notice a bluish or clear dome-shaped bump on your child’s gum right where you would expect a tooth to come in, an eruption cyst is the most likely explanation. Keeping the area clean and letting the tooth do its work is usually all that is needed.