Sebaceous Cyst: Symptoms, Causes and Diagnosis
Learn about sebaceous cysts, including their symptoms, causes, and how they are diagnosed, to better understand this common skin condition.
Written by Dr. Vasanthasree Nair
Reviewed by Dr. Shaik Abdul Kalam MD (Physician)
Last updated on 9th Sep, 2025
Introduction
Discovering a new lump under your skin can be an unsettling experience. While often harmless, it’s natural to wonder what it is and what to do about it. One of the most common types of these skin growths is a sebaceous cyst. Contrary to popular belief, most lumps called sebaceous cysts are actually epidermoid cysts, but both share similar characteristics. These slow-growing, non-cancerous bumps form just beneath the skin and are typically filled with a soft, cheese-like material called keratin. This comprehensive guide will walk you through everything you need to know: from identifying the classic signs of a sebaceous cyst and understanding what causes them, to the straightforward diagnosis process. We’ll also cover when it’s crucial to seek professional medical advice to ensure your peace of mind and skin health.
What Exactly is a Sebaceous Cyst?
A sebaceous cyst is a closed sac under the skin, classified as a type of benign skin cyst. It's essential to understand that true sebaceous cysts, which originate from oil-producing (sebaceous) glands, are quite rare. The vast majority of cysts commonly referred to by this name are actually epidermoid cysts, which originate from the skin surface (epidermis). Both types present similarly as movable lumps beneath the skin and are treated in much the same way.
Sebaceous Cyst vs. Epidermoid Cyst: Clearing the Confusion
The key difference lies in their origin. An epidermoid cyst forms when surface skin cells move deeper into the skin and multiply, creating a sac filled with keratin. A true sebaceous cyst forms from the glands that secrete oily sebum. For practical purposes, the term "sebaceous cyst" is used universally, even if it's a slight misnomer. The treatment and concerns for both are nearly identical.
The Role of Keratin in Cyst Formation
Keratin is a tough, fibrous protein that is a key structural component of hair, skin, and nails. Inside a cyst, skin cells produce keratin, which fills the sac. This material is typically thick, yellowish, and can have a faint, sometimes unpleasant odor. It is this buildup of keratin that causes the cyst to slowly enlarge over time.
Consult a Dermatologist for the best advice
Primary Signs and Symptoms of a Sebaceous Cyst
Recognizing the signs of a sebaceous cyst is the first step toward identification. Most cysts are straightforward to spot based on their appearance and feel.
Visual Characteristics and Feel
A sebaceous cyst typically appears as a smooth, dome-shaped lump under the skin, often flesh-colored or slightly yellow. It feels firm but can be gently compressed and is usually movable. In some cases, the skin over the cyst may have a small central opening or punctum.
Recognising an Infected Sebaceous Cyst
An infected sebaceous cyst may become red, swollen, and painful. It can feel warm to the touch and may produce pus or a foul-smelling discharge. In some cases, infection can lead to tenderness and surrounding skin irritation, requiring medical attention.
What Causes a Sebaceous Cyst to Develop?
Understanding the causes can help in prevention and management. The development is often linked to a blockage or damage.
Damaged Hair Follicles and Trauma
The most common cause is a damaged or irritated hair follicle. This can happen due to:
Skin Trauma: A scratch, a surgical wound, or a blow to the skin can push surface cells deeper, triggering cyst formation.
Acne: Inflammatory acne can damage follicles and glands.
Genetic Conditions: Certain inherited syndromes, like Gardner's syndrome, make a person more prone to developing various types of cysts.
How is a Sebaceous Cyst Diagnosed?
The diagnosis of a sebaceous cyst is usually a simple and quick process. If you notice a persistent lump, a doctor can provide a definitive answer.
The Physical Examination: A Doctor's First Step
In most cases, a healthcare professional, often a dermatologist or general practitioner, can diagnose a cyst simply by looking at it and feeling it. They will assess its size, mobility, and check for signs of infection. They will also ask about your medical history and how long the lump has been present.
When Further Diagnostic Tests Are Needed
Typically, tests are not required. However, if the cyst has an unusual appearance, grows very rapidly, or the diagnosis is uncertain, further investigation may be recommended.
The Role of Ultrasound Imaging: An ultrasound can help visualise the cyst's contents, confirming it is fluid-filled (cystic) and not a solid mass. It helps map the cyst's extent before removal.
Biopsy and Histopathology for Rare Cases: If there is any suspicion that the growth might be something else, like a malignant tumor, the doctor will perform a biopsy. This involves removing the entire cyst or a small sample and sending it to a lab for analysis to confirm it is benign.
Common Misdiagnoses: Conditions That Mimic Sebaceous Cysts
Not every lump under the skin is a cyst. Other conditions can present similarly, including:
Lipomas: Soft, fatty tumors that are also benign but feel doughier and are located deeper.
Boils (Furuncles): Painful, pus-filled bumps caused by an infected hair follicle. They come on more quickly than cysts.
Skin Abscesses: A collection of pus that can form from an infected cyst or other skin injury.
This is why a professional diagnosis is key. If you are unsure about a lump on your body, consulting a doctor online with Apollo24|7 can provide initial guidance and help you determine if a physical visit is necessary.
Conclusion
Discovering a sebaceous cyst can be worrying, but in the vast majority of cases, it is a harmless condition that may not require any intervention at all. By understanding the signs of a sebaceous cyst, such as a slow-growing, movable lump under the skin, you can identify them early. The diagnosis process is straightforward, providing quick clarity and peace of mind. Remember, the most important step is to avoid self-treatment, like squeezing, which can do more harm than good. Monitor the cyst for any changes, especially signs of infection like redness, pain, and swelling. If you have any concerns about a skin growth, or if a cyst is causing you discomfort, the best course of action is to consult a healthcare professional for an accurate assessment and to discuss the best management options for your specific situation.
Consult a Dermatologist for the best advice
Consult a Dermatologist for the best advice
Dr. S Madhuri
Dermatologist
10 Years • MBBS, MD. DVL, DNB, Fellow (Dermatosurgery & Lasers)
Secunderabad
Apollo Hospitals Secunderabad, Secunderabad
(400+ Patients)
Dr. Madhab Datta
Dermatologist
5 Years • MBBS, MD (DVL)
Kolkata
Dr. Madhab Datta's Clinic, Kolkata
Dr.j Girishma
Dermatologist
6 Years • MBBS MD DERMATOLOGY
Bengaluru
Apollo Medical Center, Marathahalli, Bengaluru
Dr. Indraneel Saha
Dermatologist
10 Years • MBBS, MD (WBUHS)
Kolkata
Dr Utsa Basu Clinic, Kolkata
Dr. Lakshmi B Kartha
Dermatologist
8 Years • MBBS(JIPMER), MD(JIPMER), MRCP SCE(UK) Dermatology, German board certified dermatologist- Facharzt,European board certified dermatologist
Kozhikode
Dr.Lakshmi, Kozhikode
(25+ Patients)
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Frequently Asked Questions
1. Can a sebaceous cyst go away on its own?
No, once formed, a cyst will not disappear on its own. The capsule (sac wall) remains under the skin, and while the contents might sometimes be reabsorbed, the cyst itself typically persists and may refill.
2. What is the difference between a cyst and a boil?
A cyst is a slow-growing, often painless sac filled with keratin. A boil is an acute infection of a hair follicle that appears quickly, is very painful, and is filled with pus. Boils are more red and inflamed.
3. Is it safe to drain a sebaceous cyst at home?
Absolutely not. Attempting to drain or pop a cyst at home greatly increases the risk of infection, inflammation, and scarring. It also almost guarantees that the cyst will recur because the sac wall is left behind.
4. How can I tell if my sebaceous cyst is infected?
Look for increased redness, warmth, tenderness, pain, and swelling around the cyst. You might also see pus drainage or develop a fever. These are clear signs you need to see a doctor.
5. Will removing a sebaceous cyst leave a scar?
Yes, any surgical procedure on the skin can leave a scar. However, a doctor will make every effort to minimise scarring by making incisions along natural skin lines and using precise techniques. The scar often fades significantly over time.