A sebaceous cyst is a slow-growing, noncancerous bump that forms just beneath the skin. Despite the name, most lumps called “sebaceous cysts” are technically epidermoid cysts or epidermal inclusion cysts, meaning they’re filled with a buildup of the protein keratin rather than oily sebum. The distinction rarely matters in everyday life, but it explains why your doctor might use a different term than you expect. These cysts are common, generally harmless, and range from about a quarter-inch to over two inches across.
What Actually Forms Under the Skin
Your skin constantly sheds dead cells from its surface. Normally those cells flake away unnoticed. An epidermoid cyst forms when skin cells get pushed inward instead of shedding outward, often because a hair follicle is damaged, clogged, or irritated. The trapped cells continue to produce keratin, a tough structural protein, and that material accumulates inside a sac-like pocket. Over weeks or months, the pocket slowly expands.
True sebaceous cysts (called steatocystomas) do exist, but they’re far less common. They originate from the oil-producing glands attached to hair follicles and contain a yellowish, oily substance. In a large analysis of over 1,160 benign skin cysts, steatocystomas accounted for only four cases, while epidermal inclusion cysts made up the vast majority. So when people say “sebaceous cyst,” they almost always mean an epidermoid cyst.
Who Gets Them
These cysts can appear at virtually any age, from childhood into the 90s, but they’re most common between ages 31 and 40. In that same large study, women made up about 58% of epidermal inclusion cyst cases and men about 42%. There’s no single risk factor, though cysts tend to develop more easily in areas where skin experiences friction, minor trauma, or acne. People with certain genetic conditions, like Gardner syndrome, may develop multiple cysts.
How to Identify One
A sebaceous cyst typically looks like a round, dome-shaped lump sitting just under the skin. It moves easily when you press on it, which distinguishes it from deeper or fixed masses. The texture feels firm but slightly compressible, not hard like bone and not soft like fluid.
One hallmark feature is a tiny dark dot at the center called a punctum. This is a small, plugged opening that connects the cyst to the skin’s surface. Not every cyst has a visible punctum, but when present, it’s a strong clue. The skin over the cyst usually looks normal, though it can turn pink, red, or darker than your surrounding skin tone if the cyst becomes irritated.
Size varies widely. Most cysts stay small, under an inch, but some grow to two inches or more. Growth is typically very gradual. If you notice a lump that appeared overnight or is growing rapidly, that’s less likely to be a simple cyst and worth getting checked.
Where They Commonly Appear
Sebaceous cysts favor areas with dense concentrations of hair follicles. The face, neck, scalp, and upper back are the most frequent locations. They also show up on the chest, shoulders, and behind the ears. Cysts can develop nearly anywhere on the body except the palms and soles, which lack hair follicles entirely.
When a Cyst Becomes a Problem
Most cysts cause no symptoms at all. They sit quietly under the skin for months or years, and many people leave them alone indefinitely. Problems arise when a cyst becomes inflamed or infected. The signs are hard to miss: the area swells, turns red or warm, becomes tender, and sometimes produces a thick, foul-smelling discharge if the cyst ruptures beneath or through the skin.
Inflammation doesn’t always mean infection. A cyst can rupture internally, leaking keratin into surrounding tissue, which triggers an intense inflammatory reaction even without bacteria. The result looks and feels a lot like an infection, with redness, swelling, and pain. Either way, an inflamed cyst needs medical attention rather than a wait-and-see approach.
Cysts occasionally recur after treatment if any part of the sac wall is left behind. The remaining lining continues producing keratin, and over time the cyst refills. This is the most common complication of incomplete removal.
Why You Shouldn’t Squeeze or Pop It
It’s tempting to treat a cyst like a large pimple, but squeezing it at home creates real problems. The pressure can rupture the cyst wall internally, pushing keratin into deeper tissue and sparking the kind of inflammatory reaction described above. It can also introduce bacteria through broken skin, converting a painless lump into a genuine infection. And even if you manage to express some contents, the sac lining stays intact, so the cyst will almost certainly refill.
Warm compresses applied to the area can sometimes encourage a cyst to drain on its own through its natural opening. This is the safest thing you can do at home for a cyst that’s bothering you. A clean cloth soaked in warm water, held against the cyst for 10 to 15 minutes a few times a day, may help. If the cyst doesn’t respond or becomes painful, that’s when professional removal makes sense.
How Removal Works
The three most common reasons people have a cyst removed are repeated inflammation, cosmetic concerns, and simple annoyance from the lump catching on clothing or jewelry. Removal is a minor outpatient procedure done under local anesthesia.
The goal is to take out the entire cyst wall in one piece. If the sac is removed completely, recurrence is unlikely. The procedure involves a small incision, careful separation of the cyst from surrounding tissue, and closure with stitches. Some clinicians use a minimal-incision technique or a small punch tool to extract the cyst through a smaller opening, which can leave a less noticeable scar.
Timing matters. Doctors generally avoid removing a cyst while it’s actively inflamed, because swollen tissue makes it harder to cleanly separate the sac, and the recurrence rate goes up. The standard approach is to wait at least four weeks after inflammation has settled before scheduling excision. If a cyst is severely swollen with fluid buildup, a doctor may drain it first to relieve pressure, but this is considered a temporary measure. Draining alone doesn’t cure the cyst, and it can make the eventual removal more difficult because of scar tissue.
Recovery after excision is straightforward. The site needs basic wound care for a week or two, and stitches typically come out within 7 to 14 days depending on the location. Scarring is minimal for most small cysts, though larger ones or cysts on the face may leave a more visible mark.
Cysts That Deserve a Closer Look
The vast majority of sebaceous cysts are completely benign. However, a few features warrant prompt evaluation: a lump that grows quickly (over days rather than months), a diameter larger than two inches, a cyst that returns repeatedly after removal, or a lump that feels fixed in place rather than mobile. In rare cases, skin cancers can mimic the appearance of a cyst, so any lump with unusual characteristics is worth having a clinician examine. Removed cysts are routinely sent for pathology to confirm the diagnosis.