Pilar Cysts
Smooth, harmless lumps that usually form on the scalp
Quick Facts
- Type: Benign skin cyst
- Most common site: Scalp
- Filled with: Keratin from hair follicle lining
- Nature: Harmless; often run in families
Overview
Pilar cysts are common, noncancerous lumps that develop from hair follicles, most often on the scalp. Also called trichilemmal cysts or wens, they form a smooth sac filled with keratin produced by the lining of the hair root. Because the scalp has so many hair follicles, this is the usual location, though they can occasionally appear elsewhere.
Pilar cysts are firm, smooth, and usually painless, and they often run in families. People may have one or several. They are harmless and do not turn into cancer, but they can grow large enough to be noticeable or to catch a comb, and they are sometimes removed for comfort or cosmetic reasons. Pilar cysts are closely related to the epidermoid cyst and the broader group of epidermal cysts, though they arise from a different part of the hair follicle.
Because they sit on the scalp and are usually hidden by hair, pilar cysts are often discovered by chance, such as while combing or washing the hair. They tend to grow slowly and remain harmless, but their location can make them prone to catching on a comb or brush. When a pilar cyst becomes bothersome, removal is straightforward and the firm sac usually comes out cleanly.
Symptoms
Pilar cysts have a recognizable appearance:
- Smooth, firm, dome-shaped lumps under the skin
- Most often on the scalp, where they may be felt through the hair
- Usually painless and slow-growing
- Skin over the cyst is typically normal, without a visible central pore
- Often multiple, and they may run in families
- Can become tender, red, or swollen if inflamed or infected
A pilar cyst that grows quickly, becomes painful, or breaks down should be checked, both to manage symptoms and to confirm it is benign.
Causes
Pilar cysts form from the outer lining of a hair follicle:
- Keratin buildup: Cells from the hair root sheath produce keratin that accumulates inside a closed sac.
- Genetics: They commonly run in families, and a tendency to develop multiple cysts can be inherited.
- Hair-bearing skin: They favor the scalp because of its dense hair follicles.
They are not caused by poor hygiene and are not contagious. Unlike some other cysts, pilar cysts usually do not have a visible opening on the skin surface.
Risk Factors
- A family history of pilar cysts
- Adulthood and middle age
- Being female (somewhat more common)
- Having had pilar cysts before, which makes new ones more likely
Diagnosis
Pilar cysts are usually diagnosed by examination:
- Physical exam: A doctor can often identify a pilar cyst by its smooth, firm feel and scalp location.
- Imaging: Occasionally ultrasound is used for larger or deeper lumps.
- Pathology: If a cyst is removed, the tissue may be examined to confirm the diagnosis.
The diagnosis is usually clear from the examination, and most pilar cysts do not require extensive testing.
Treatment
Pilar cysts often need no treatment. When treatment is wanted, options include:
- Observation: Leaving a small, painless cyst alone.
- Surgical removal: A doctor removes the whole cyst, which usually comes out cleanly and intact, reducing the chance it returns.
- Managing inflammation or infection: An inflamed or infected cyst may need drainage and sometimes antibiotics, with removal planned afterward.
It is best not to try to squeeze or remove a cyst at home, since this can cause infection, bleeding, and recurrence.
Self-Care
- Avoid squeezing or picking at the cyst
- Be gentle when combing or brushing over a scalp cyst
- Keep the area clean to reduce infection risk
- Watch for redness, warmth, or pain that may signal infection
- See a doctor for removal if a cyst is enlarging or bothersome
When to See a Doctor
See a doctor if a scalp or skin lump grows, becomes painful, red, or swollen, starts draining, or keeps catching when you comb your hair, or if you want it removed. Have any new or unusual lump evaluated to confirm it is benign. Seek prompt care for spreading redness, fever, or significant pain, which can indicate an infection needing treatment.
Frequently Asked Questions
Are pilar cysts dangerous?
No, pilar cysts are benign and do not turn into cancer in the vast majority of cases. They are harmless keratin-filled sacs that usually form on the scalp. A cyst that grows rapidly, becomes painful, or looks unusual should still be checked by a doctor.
How are pilar cysts different from other cysts?
Pilar cysts form from the lining of the hair follicle and usually appear on the scalp, often without a visible central pore. Epidermoid cysts more often appear on the face, neck, and trunk and may have a small surface opening. Both are filled with keratin and are benign.
Why do pilar cysts run in families?
There is an inherited tendency to develop pilar cysts, so they often affect several members of the same family and can appear as multiple cysts. The exact genetic basis varies, but a family history makes them more likely.
Can a pilar cyst be removed?
Yes. A doctor can remove a pilar cyst, and because the sac is usually firm, it often comes out cleanly and intact. Removing the whole cyst reduces the chance it returns. Removal is typically done for comfort, growth, or cosmetic reasons.
Should I try to pop a pilar cyst at home?
No. Squeezing or trying to pop a cyst can cause infection, bleeding, scarring, and make it more likely to return. If a pilar cyst bothers you or becomes inflamed, see a doctor for proper drainage or removal.
References
- American Academy of Dermatology (AAD). Cysts: Overview.
- MedlinePlus, U.S. National Library of Medicine. Skin cyst.
- DermNet. Trichilemmal (pilar) cyst.
- Mayo Clinic. Skin lumps and cysts.