Condition

Pilar Cyst

A pilar cyst is a smooth, firm lump under the skin of the scalp, filled with keratin from a hair root. It is harmless, it runs in families, and it does not go away on its own.
At a Glance

A pilar cyst is a smooth, firm, mobile lump that grows from the root of a hair follicle, almost always on the scalp. They are harmless, usually painless, often multiple, and they run strongly in families.

They are not the same as epidermoid cysts, which turn up more often on the face, neck and trunk and usually have a visible dark pore in the middle.

The honest catch: they do not disappear, squeezing does not empty them and risks rupture and infection, and the only thing that removes one for good is taking out the whole sac.

Key Facts

How CommonCommon. Roughly 5 to 10 percent of people have at least one.
Who Gets ItAdults, more often women, and often several people in the same family. Most common in middle age.
Chronic or CurableCurable by removal. They do not resolve on their own.
Rx RequiredNo. Removal is a minor procedure rather than a prescription.
ContagiousNo.
CostRemoval is a minor surgical procedure, usually a few hundred dollars. Insurance often covers it when a cyst is painful, inflamed, or catching on a comb. A purely cosmetic removal may not be covered.

Symptoms

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A pilar cyst is usually found by touch rather than seen — a smooth bump under the fingers while washing or brushing the hair.

What it looks and feels like

A firm, smooth, round lump — under the skin rather than on it.
It moves — you can slide the skin and the lump together over the bone underneath. That mobility is characteristic.
Skin-coloured, with normal skin stretched over it and hair usually growing over it as normal.
No central pore — epidermoid cysts often have a small dark opening in the middle. Pilar cysts usually do not.
Painless, unless it becomes inflamed.
Often more than one, and often growing very slowly over years.
Thick, pale, cheesy contents with a distinct smell if one ruptures. That is keratin, the same protein as hair and nails, not pus.
When inflamed — suddenly sore, discoloured, swollen and warm over a day or two.

Where it shows up

  • The scalp, in roughly 90 percent of cases.
  • Occasionally the face, neck, back or anywhere else with hair.
  • Almost never on palms or soles, which have no hair follicles.

How it looks on different skin tones

The lump itself looks the same whatever your skin tone, because the skin over it is normal. When one becomes inflamed, the redness that is obvious on light skin may look brown, purple or simply darker on brown and Black skin, so tenderness, warmth and swelling are more reliable signs. After an inflamed cyst settles or is removed, the skin can be left darker for months, and scalp scars are more likely to become raised or keloid in people prone to that.

Light
Medium
Brown
Deep

If your lump does not fit this description, see Lookalikes near the bottom of this page.

Causes & Risk Factors

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A pilar cyst grows from the outer root sheath of a hair follicle, which is the layer of cells wrapped around a hair below the surface. Those cells make keratin, the tough protein in hair and nails. If a pocket of them becomes closed off, they carry on producing keratin into a sealed sac with nowhere to drain. The keratin builds up slowly and the sac stretches into a firm lump. That explains the two things people most want to know: why the contents are thick and pale rather than liquid, and why the lump does not shrink on its own. There is no route out.

The strongest risk factor is family history. Pilar cysts are inherited in many families in a straightforward dominant pattern, which is why people often have several and often have a parent or sibling with them. They are not caused by poor hygiene, shampoo, hats, or anything you did. An injury to the scalp can occasionally trigger one, but most appear for no identifiable reason.

What Hurts and What Helps

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What Makes It Worse

  • Squeezing. A pilar cyst sits inside a tough sac, and pressure does not empty it. It ruptures the sac inward instead, spilling keratin into the surrounding tissue and setting off an intense inflammatory reaction. That is what turns a painless lump into a hot, painful one overnight.
  • Picking, needling or trying to lance one at home. The same problem, with infection added and a worse scar afterwards.
  • Repeated friction from a comb, a hairbrush, a helmet strap, tight braids or a hat catching the same spot.
  • Waiting until it is inflamed to have it removed. An inflamed cyst is harder to take out cleanly, the sac tears more easily, and it is more likely to come back.
  • Not much else. Diet, hygiene, hair products and shampoo do not affect them.

Daily Habits That Help

  • Leaving it alone. A pilar cyst that does not bother you does not need treating. There is no medical reason to remove one, and watching it is a legitimate choice.
  • Warm compresses if one becomes tender. They ease the discomfort while it settles. They will not drain it or shrink it.
  • Ibuprofen for a few days if an inflamed one is sore.
  • Having it removed properly when you do want it gone. Removal means taking out the entire sac, not just the contents. Pilar cysts are unusually cooperative here — the sac is tough enough that it often shells out whole through a small incision, which is why they come back less often than epidermoid cysts do.
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  • Timing it well. If one has flared, it is usually better to let the inflammation settle and remove it a few weeks later, when the sac is intact and the whole thing comes out cleanly.

Try at Home

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There is no home treatment that removes a cyst. These are for comfort if one becomes inflamed, and for resisting the urge to squeeze it.

Always
A perfectly reasonable choice. A pilar cyst that does not hurt, does not catch and does not bother you needs no treatment at all. Just do not squeeze it — that is what turns a quiet lump into a painful one.
Moderate evidence
Useful for the few days when a cyst has ruptured internally and become hot and sore. It takes the pain and swelling down while the inflammation settles. It does nothing to the cyst itself.
Limited evidence
Comfortable on an inflamed cyst, and worth doing for that reason. Be clear about what it will not do: it does not shrink a cyst, drain it, or make it go away. There is no route out through intact skin.
Limited evidence
Only relevant if a cyst has ruptured through the skin and is draining. Keep the area clean and covered. It does not treat the cyst, and it is not a reason to open one yourself.
Limited evidence
Widely recommended online for cysts, and it does not work. Nothing applied to the surface reaches inside a closed sac under the skin. There is no evidence it shrinks or dissolves a cyst, and undiluted tea tree oil irritates the scalp. It is listed here because people try it, not because it helps.

When to See a Dermatologist

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There is no need to have a pilar cyst looked at simply because it exists. It is worth booking a visit if:

  • It is painful, discoloured, swollen or growing quickly.
  • It has ruptured or is draining.
  • It catches on a comb or brush, or sits where a helmet or hairband presses.
  • It is larger than a few centimetres, or growing noticeably faster than it used to.
  • It feels unusual — hard and fixed to the tissue underneath, ulcerated, or bleeding.
  • You simply want it gone. That is a good enough reason on its own.

What the visit gets you: confirmation that it is what you think it is, and removal of the entire sac in one small procedure under local anaesthetic. That is the only thing that gets rid of one permanently.

Prescription Treatments

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Only relevant if a cyst is genuinely infected or badly inflamed. Neither of these makes the cyst go away.

Topical prescriptions
Limited evidence
Used on a cyst that has genuinely become infected at the surface, or on the skin after one has been drained. It has no effect on an intact cyst underneath.
Pills and injections
Limited evidence
Prescribed when an inflamed cyst really is infected, with spreading redness, warmth or fever. Worth knowing that most sudden painful cysts are ruptured rather than infected, so antibiotics are given more often than they are needed and frequently do not help.
Pills and injections
Limited evidence
Sometimes used for an inflamed cyst as much for its anti-inflammatory effect as its antibiotic one. The evidence in cysts specifically is thin, and it does not remove the sac, so the lump is still there afterwards.

In-Office Treatments

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The only treatments that actually remove a pilar cyst. Which one you get depends on whether the cyst is calm or inflamed right now.

Strong evidence
The only thing that removes a pilar cyst for good. Local anaesthetic, a small incision, and the whole sac lifted out intact. Pilar cysts are unusually cooperative — the sac is tough, so it often shells out whole, which is why they come back less often than epidermoid cysts. Fifteen to thirty minutes, a few stitches, and a thin scar hidden in the hair.
Moderate evidence
A smaller-scar version. A tiny circular blade makes a hole, the contents are expressed, and the sac is teased out through the opening. It leaves less of a mark, and it suits small, uninflamed cysts. The trade-off is a slightly higher chance of leaving sac behind, which means it can come back.
Moderate evidence
For a cyst that is acutely swollen and painful. It relieves the pressure quickly and is the right call when one has flared. It is not a cure — the sac stays behind, so the lump comes back, and the plan is usually to remove it properly a few weeks later once everything has settled.
Moderate evidence
A small injection of steroid into an inflamed cyst settles the swelling and pain over a few days, often without needing to cut into it. It does not remove the cyst, and it is used to calm things down before proper removal.
Moderate evidence
Not needed for an ordinary pilar cyst, which is recognised on sight. It matters for one that has grown large, become lumpy, or ulcerated, because that can be a proliferating pilar tumour, which needs full removal and examination under the microscope. Removed cysts are often sent for checking as routine.

What to Expect

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Step 1
If you leave it alone

Nothing much happens. Most pilar cysts grow very slowly over years, and plenty stay the same size indefinitely. There is no harm in watching one.

Step 2
If it becomes inflamed

It swells, discolours and becomes sore over a day or two. Most settle over one to three weeks with warm compresses and time. Some are drained in the office for immediate relief, which helps the pain but leaves the sac behind, so the lump returns.

Step 3
The day of removal

Local anaesthetic, a small incision, and the sac lifted out whole. Usually fifteen to thirty minutes. You feel pressure and pulling, not pain.

Step 4
The first two weeks

A few stitches, kept dry for a couple of days and removed at around ten to fourteen days on the scalp. Mild soreness for a few days. Hair covers the site quickly.

Step 5
Long term

A thin scar hidden in the hair, and no lump. If the entire sac came out, it does not come back in that spot. Because pilar cysts run in families, new ones can appear elsewhere over the years. That is not a failure of the removal.

Step 6
The honest long view

They are harmless. Removal is a choice, not a medical necessity, and the main argument for doing it sooner is that a calm cyst comes out far more cleanly than an inflamed one.

Complications

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Pilar cysts are benign and stay benign. The complications are local ones.

Rupture and inflammation
The most common problem by far. The sac breaks, usually after being squeezed or knocked, and keratin leaks into the surrounding tissue. The result is a hot, painful, swollen lump that looks infected but usually is not. It is an inflammatory reaction to the contents, and it is often treated with drainage or a steroid injection rather than antibiotics.
Genuine infection
Less common, and usually follows attempts to squeeze or open one at home.
Recurrence
If any of the sac wall is left behind, the cyst reforms. This is why removal takes out the whole sac rather than just emptying it.
Scarring
A small scar is the trade for removal. On the scalp it hides in the hair. In people prone to keloids, a raised scar is possible.
Catching and pressure
Larger cysts get caught by a comb, sit awkwardly under a helmet, or make hairstyling uncomfortable.
Proliferating pilar tumour
Rare. A pilar cyst that grows large, becomes lumpy or ulcerates can turn into this thicker, more solid growth. It is almost always benign, but it can behave aggressively in the local area, so it needs full surgical removal and examination under the microscope. Very rarely it becomes malignant. This is the reason a cyst that suddenly grows or changes should be looked at rather than watched.

Lookalikes

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Several kinds of lump turn up under the skin. Location and feel usually separate them.

  • Epidermoid cyst — the other common cyst, and the one pilar cysts are most often confused with. More often on the face, neck, chest or back than the scalp, usually with a small dark central pore, and the contents smell worse. Treated the same way, though the sac is more fragile and it comes back a little more often.
  • Lipoma — a soft, squashy, mobile lump of fat, usually deeper and less well-defined than a cyst, with no pore. See cyst vs lipoma.
  • Abscess — an infected collection of pus. Painful, hot, discoloured and growing over days rather than years. See abscess vs cyst.
  • A deep pimple or boil — inflamed, tender and short-lived, settling in a week or two. A cyst is a lump that has been there for months. See cyst vs pimple.
  • Osteoma of the skull — a hard bony lump on the scalp that does not move when you slide the skin over it. Cysts move with the skin; this does not.
  • Enlarged lymph node — on the neck or behind the ear rather than the top of the scalp, rubbery, and often appearing during an infection.
  • Dermatofibroma — a small firm lump, usually on the legs, that dimples inward when you pinch it.

The pilar cyst pattern is: scalp, smooth, firm, mobile, no pore, painless, often more than one, and usually someone else in the family has them too.

FAQ+
Are pilar cysts dangerous?No. They are benign collections of keratin and they stay benign. The rare exception is a proliferating pilar tumour, which is a cyst that grows large or changes and should be checked.
Will a pilar cyst go away on its own?No. There is no way out for the contents, so the sac does not empty or shrink. It can stay the same size for years, but it does not disappear.
Can I pop or squeeze it?No. The sac is tough, and pressure ruptures it inward instead of emptying it. That spills keratin into the tissue and causes a painful inflamed lump, plus a risk of infection and a worse scar.
What is the difference between a pilar cyst and an epidermoid cyst?Location and structure. Pilar cysts grow from the hair root, are usually on the scalp, and have no central pore. Epidermoid cysts are more often on the face, neck and trunk, and usually have a visible dark pore in the middle.
Why do I have several?Because they run in families. Pilar cysts are inherited in many families, which is why people often have multiple cysts and a parent or sibling with them.
Does removal leave a bald patch?Usually not. The incision is small and hair grows back around a thin scar. A large cyst leaves a longer scar, which is another argument for removing one while it is still small.
Will it come back after removal?Not in the same spot, if the entire sac was taken out. Pilar cyst sacs are tough and tend to shell out whole, so recurrence is uncommon. New cysts can appear elsewhere over the years.
My cyst suddenly became painful. Is it infected?Usually not. Most sudden pain is rupture with inflammation rather than infection. The treatment is different, so antibiotics often are not the answer, and drainage or a steroid injection may be.
Can it be drained instead of cut out?It can be drained if it is inflamed and painful, and that helps quickly. But draining leaves the sac in place, so the lump comes back. Drainage is for relief; removal is for cure.
Do creams, tea tree oil or drawing salves work?No. Nothing applied to the surface reaches inside a closed sac under the skin. Tea tree oil is popular for this and there is no evidence it does anything to a cyst.
Should I have it removed if it does not bother me?You do not have to. Leaving it alone is a reasonable choice. The practical argument for removing one is that small, calm cysts come out more easily and leave smaller scars than large or inflamed ones.
Is it caused by shampoo, hats or not washing my hair?No. It comes from a hair follicle and, most often, from your genes.