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Almost everyone calls these sebaceous cysts, but what you almost certainly have is an epidermoid cyst - a small closed bag lined with skin cells, quietly filling with keratin. It is not oil, not an infection, and not cancer.
A quiet cyst comes out neatly in one appointment with a small scar; an inflamed one tears instead of lifting out whole and leaves a bigger scar, so if it has flared once, plan removal for after it settles.
And please do not squeeze it - pressure ruptures the sac inward, and most of the angry, painful cysts I see were squeezed the day before.
— Dr. Schwarz, Board Certified Dermatologist
Key Facts
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| How common | One of the most common lumps in the skin - most people will have one at some point |
| Who gets it | Adults, most often between about 20 and 60, and somewhat more often in men |
| Curable or managed | Curable - but only by removing the whole sac. Draining it empties it without ending it |
| Prescription needed | Not for a quiet cyst. An inflamed one may need a steroid injection, drainage, or antibiotics if it is truly infected |
| Time to improve | An inflamed cyst usually settles over one to two weeks. Removal is a single minor procedure |
What It Is
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An epidermoid cyst is a closed sac under the skin, lined with the cells that make up the skin surface. Those cells shed keratin inward, into a sealed space, so over months and years the sac fills with soft, pale, cheesy keratin and the lump enlarges.
From outside it is a firm, smooth, dome-shaped lump, skin-colored or slightly yellow, that moves a little when you push it because it sits within the skin rather than fixed to what is underneath. Many have a small dark dot at the center - a punctum, the blocked opening it formed from. Sizes run from a pea to several centimeters; usually painless.
The contents are keratin and broken-down cells, not oil. Squeezed out it is pale, pasty and foul-smelling, which is why people assume it is infected when it is not. Other names are epidermal inclusion cyst, infundibular cyst and keratin cyst.
Common sites are the face, neck, upper back, chest, behind the ear and the scrotum. A close relative, the pilar cyst, grows from the root sheath of a hair on the scalp, where it is firmer, smoother and easier to remove whole.
Hold on to the difference between a quiet cyst and an inflamed one. A quiet cyst is just a lump. An inflamed one is red, hot, swollen and painful, usually because the wall ruptured and spilled keratin into surrounding tissue, which the immune system attacks hard. That reaction is chemical rather than bacterial most of the time, which is why antibiotics often disappoint. A cyst can also become genuinely infected, and telling those apart is what a clinic visit is for.
Symptoms
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Quiet Cyst
Inflamed
Discharging
How It Looks by Skin Tone
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The cyst is the same on every skin tone, but two things read differently on deeper skin tones.
The first is spotting a flare. On deeper skin tones an inflamed cyst often looks brown, violet or simply darker rather than red. The signs that carry more weight are heat, swelling, tenderness out of proportion to the lump, and skin over it that feels tight or shiny. Waiting to see redness means waiting too long. The second is scarring. Deeper skin tones are more prone to raised, thickened scars - hypertrophic scars and keloids - and to dark marks after inflammation or surgery. The chest, shoulders, upper back and jawline are the highest-risk sites, and also common cyst sites. Have that conversation before removal: ask how the incision will be placed, whether it follows the natural skin lines, and what the scar plan is afterward - silicone sheets or gel, taping, or a steroid injection into the healing scar. None of that is a reason to leave a cyst that keeps flaring. Each rupture and each drainage makes its own inflammation and its own scar, so repeated flares leave more marking than one planned removal. Take it out while it is quiet, by someone who has thought about the incision. Sun protection over a healing scar is worth the effort, because ultraviolet light darkens new scars and makes the mark last much longer.
Where It Shows Up
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What Happens in the Skin
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This is what is going wrong under the skin, in the order it happens. Click a step to see it.
How Epidermal Inclusion Cyst happens
Skin basics
A hair follicle is an open tube, and the cells lining it are the same kind that make up the skin surface. They shed keratin the way they always do, upward and out through the opening, where it flakes away unnoticed. Nothing collects inside, because the tube stays open at the top.
The opening of a hair follicle plugs and the lining underneath seals over into a closed pocket. Sometimes it starts a different way, when an injury such as a cut, a piercing or surgery pushes a fragment of skin surface down into the deeper layers.
The sac is lined with cells that behave exactly like the skin surface, so they keep shedding keratin — inward, into a sealed space with no way out. The lump enlarges slowly over months and years, which is why a cyst never simply goes away.
Under pressure from squeezing or friction, or sometimes for no clear reason, the wall tears and keratin leaks out into the surrounding tissue. Nearly every bad outcome on this page runs through this step — a cyst that never ruptures is just a lump.
The immune system treats loose keratin as foreign material and attacks it hard, which is what produces the sudden heat, swelling and pain — usually with no bacteria involved at all. Each episode leaves scar tissue behind that tethers the sac and makes it harder to remove cleanly.
The outer film of dead cells and oil. It holds water in and keeps irritants out, and it is thinner than a sheet of paper. Almost every dry, itchy, stinging skin problem starts here.
The outer layer, and the only one anything in a jar reaches. It renews itself constantly: a cell made at the bottom takes about a month to reach the surface and flake off. Most of what a skincare product does, it does here.
The living layer underneath, holding the blood vessels, the nerves and the collagen. It is where lasting change happens and it is hard to reach: most of what is sold for the skin never gets this far.
A cyst starts one of two ways. Most often a hair follicle opening plugs and the lining below it seals over into a closed pocket. Less often an injury - a cut, a puncture, a piercing, surgery - pushes a fragment of skin surface into the deeper layers, and those cells set up a sac where they land.
Either way you get a closed bag lined with cells that behave like skin surface, shedding keratin into an enclosed space. Nothing needs to leave and nothing can, so the sac slowly fills over months to years. That is why a cyst grows so slowly and never simply resolves.
The flare is a separate event. Under pressure - squeezing, friction, sometimes nothing obvious - the wall tears and keratin leaks into surrounding tissue. The immune system treats loose keratin as foreign and attacks it, producing sudden heat, swelling, redness and pain with no bacteria involved. A cyst can also be invaded by bacteria and become truly infected, which looks similar and matters, because that is the version antibiotics help.
Which is why drainage alone does not end it. Draining removes the contents, but the lining stays, and a lining that stays keeps making keratin. A permanent cure means taking out the sac wall too.
Risk Factors
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Most people who get a cyst have no particular reason for it. These make one more likely.
Course
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Left alone, a cyst sits quietly for years, punctuated by flares. The pattern matters more than any single episode - a cyst that has never flared can come out whenever it suits you, while one that has flared twice is on a trajectory. Plan removal during a quiet spell.
A slowly enlarging, painless, firm lump that moves under the skin. Many have one for a decade without thinking about it.
The wall tears, often after squeezing or friction, sometimes for no reason, and keratin escapes into surrounding tissue. The area turns hot, swollen, tender and discolored, and the lump feels larger. This is the immune system reacting to spilled keratin, not an infection.
It either subsides or comes to a head and discharges foul-smelling material, after which the pain drops.
Once the inflammation passes, the lining starts making keratin again and the lump comes back. This surprises most people.
Each flare leaves scar tissue that tethers the sac, making removal harder and the scar wider.
What Makes It Better & Worse
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Four problems in sequence - a sac forms, fills, ruptures, scars. Nearly every bad outcome runs through step three - one that never ruptures is just a lump.
What is driving yours?
The opening of a hair follicle plugs and the lining underneath seals over into a closed pocket. Sometimes it starts a different way, when an injury such as a cut, a piercing or surgery pushes a fragment of skin surface down into the deeper layers.
The sac is lined with cells that behave exactly like the skin surface, so they keep shedding keratin — inward, into a sealed space with no way out. The lump enlarges slowly over months and years, which is why a cyst never simply goes away.
Under pressure from squeezing or friction, or sometimes for no clear reason, the wall tears and keratin leaks out into the surrounding tissue. Nearly every bad outcome on this page runs through this step — a cyst that never ruptures is just a lump.
The immune system treats loose keratin as foreign material and attacks it hard, which is what produces the sudden heat, swelling and pain — usually with no bacteria involved at all. Each episode leaves scar tissue behind that tethers the sac and makes it harder to remove cleanly.
What helps
- Treat underlying acne Fewer new cysts where heavy acne is controlled.
What makes it worse
- A midline lump on a baby Identify it first - a few connect to deeper structures.
What helps
- Have it removed while it is quiet Taking out the lining is the only cure.
What makes it worse
- Having only the contents drained The lining stays, so it refills.
- Drawing salves and home remedies Nothing surface-applied dissolves a sac.
What helps
- Leave a quiet cyst alone A legitimate choice many people make for years.
- Reduce friction over it Adjust a strap, move a backpack.
- Do not squeeze it Almost every painful cyst was painless until it was pressed.
What makes it worse
- Squeezing it Pressure tears the sac from inside.
- Picking at the central dot Widens the opening, invites bacteria.
- Lancing it at home Infection risk, a scar, and the lining stays.
- Friction and pressure over it Straps and waistbands set a stable cyst flaring.
- Shaving over it A nick is a straight route to inflammation.
What helps
- A steroid injection early in a flare Settles swelling and pain in days.
- Warm compresses Ease discomfort and help it come to a head.
- Incision and drainage Fast relief for a painful flare, but it refills.
- Antibiotics for genuine infection Spreading redness, pus, fever, feeling unwell.
- Ask about the scar plan Incision placement, silicone, sun protection.
What makes it worse
- Assuming antibiotics fix a flare Flares react to keratin, not infection.
- Waiting for a flare to remove it The sac tears instead of lifting out.
- Repeated flares over years Each lays down scar tissue that tethers the sac.
How These Treatments Work
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Treatments for Epidermal Inclusion Cyst do not all work in the same place. Tap one to see where it acts.
Pick a treatment
Skin basics
Settles the swelling and redness within days. The sac stays.
Relieves the pressure. The wall is still there, so it usually refills.
Taking out the whole wall is the only thing that stops it coming back.
Most red, sore cysts are inflamed rather than infected.
The outer film of dead cells and oil. It holds water in and keeps irritants out, and it is thinner than a sheet of paper. Almost every dry, itchy, stinging skin problem starts here.
The outer layer, and the only one anything in a jar reaches. It renews itself constantly: a cell made at the bottom takes about a month to reach the surface and flake off. Most of what a skincare product does, it does here.
The living layer underneath, holding the blood vessels, the nerves and the collagen. It is where lasting change happens and it is hard to reach: most of what is sold for the skin never gets this far.
Over-the-Counter Products
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Everything here you can buy without seeing anyone.
No over-the-counter options listed yet.
Prescriptions
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These need a prescription.
No prescription treatments listed yet.
Procedures
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These are done in the office, usually over several visits.
No procedures listed yet.
When to See a Dermatologist
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Most cysts never need urgent attention; they sit for years doing nothing. Get same-day care if redness or discoloration is spreading out from the lump, if there is pus, if you have a fever or feel unwell, if it is quickly more swollen and painful, or if a cyst on the face, particularly around the nose, eyes or upper lip, turns hot and inflamed. Book promptly if a lump is growing fast, feels hard and fixed rather than mobile, bleeds, has a sore over it that will not heal, or has changed character - and book without urgency, but do book, once a cyst has flared even once, because that flare is your cue to plan removal for a quiet period. Most are diagnosed by looking and feeling - firm, smooth, dome-shaped, mobile, slow-growing, often with a small central dot - with an ultrasound when it is not obvious; taking the whole sac out during a quiet spell is the only thing that ends it.
— Dr. Schwarz, Board Certified Dermatologist
Complications
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Rupture and a painful flare
Infection or an abscess
Scars and keloids from repeat flares
Lookalikes
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Lipoma
Hidradenitis Suppurativa
Acne
Myths
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- "It is a sebaceous cyst full of oil." Almost all of these are epidermoid cysts, and the contents are keratin - shed skin protein - not sebum. True sebaceous cysts - steatocystomas - exist but are far less common. The name stuck; the biology did not.
- "Antibiotics will make it go away." Antibiotics treat bacterial infection. Most flares are the immune system reacting to keratin that leaked from a ruptured sac, with no bacteria involved. They matter for genuine spreading infection, not otherwise.
- "Squeezing it hard enough will empty it for good." Squeezing ruptures the sac inward as often as it pushes contents out, and the lining always stays. Expect a painful, swollen lump for a week and a cyst that refills anyway.
- "It is cancer." Epidermoid cysts are benign. Cancers arising within one are described and genuinely rare. Have a lump examined if it grows rapidly, feels hard and fixed rather than mobile, bleeds, or has a wound that will not heal - those suggest it is not a cyst.
- "If I leave it long enough it will turn into cancer." Time does not turn a cyst malignant. It does make it larger, more likely to flare, and harder to remove neatly.
- "Once it has been drained, it is gone." Drainage takes the contents and leaves the lining, and the lining is the cyst. It refills over weeks to months - relief, not cure.
- "There is a cream that dissolves it." Nothing on the surface reaches a sac beneath the skin. Drawing salves, essential oils and heat balms do not remove a lining, and some irritate enough to trigger a flare.
- "Removal always leaves a bad scar." Removal always leaves a scar, because the skin has to be opened. A planned excision on a quiet cyst leaves a thin line along a natural crease. The big scars come from emergency drainage during a flare, or repeated flares that scarred the area first.
Questions Patients Ask
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Is it dangerous?
Epidermoid cysts are benign. They do not spread and do not turn into cancer. Cancers arising inside a cyst are described but genuinely rare. Have it examined if it grows rapidly, feels hard and fixed rather than mobile, bleeds, or has a sore over it that will not heal - those suggest the lump may not be a cyst.
Why does it smell?
The contents are keratin and broken-down skin cells, sealed in for a long time, and skin bacteria break that material down. The smell comes from the contents, not from infection.
Can I just have it drained?
You can, and for a large, painful, inflamed cyst that is the right thing for relief. But draining empties the contents and leaves the lining, and the lining makes keratin, so it refills over weeks to months. Removing the whole sac is what ends it.
Why will my doctor not remove it while it is inflamed?
Because the result is worse. Inflamed tissue is swollen and fragile, so the sac tears instead of lifting out whole, fragments get left behind, the cyst is more likely to come back, and the scar is wider. Settle the flare first, then remove it a month or two later.
Will it come back after surgery?
Not if the whole lining comes out, which is the goal. Recurrence happens when a fragment is left behind, more likely if the cyst was inflamed or heavily scarred from previous flares. New cysts can form elsewhere - that is a new cyst, not the old one.
Can I stop getting them?
Not reliably, because most people who get one have no identifiable cause. You can reduce flares - do not squeeze them, take pressure and friction off them, and treat significant acne if cysts keep appearing where it was. If you are getting a lot from a young age, mention it, because a few people have an inherited reason.
References
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- Hoang VT, Trinh CT, Nguyen CH, et al. Overview of epidermoid cyst. European journal of radiology open. 2019. — European journal of radiology open, 2019
- Wilson JL. Benign Skin Tumors. Primary care. 2025. — Primary care, 2025
- Costa C, Barba M, Cola A, et al. Paraclitoral Epidermal Cysts: A Literature Systematic Review. Medicina (Kaunas, Lithuania). 2025. — Medicina (Kaunas, Lithuania), 2025
- Zhao A, Kedarisetty S, Arriola AGP, et al. Pilomatrixoma and its Imitators. Ear, nose, & throat journal. 2024. — Ear, nose, & throat journal, 2024
- Hood AF, Lumadue J. Benign vulvar tumors. Dermatologic clinics. 1992. — Dermatologic clinics, 1992