Cysts form when skin cells, keratin, fluid, or other material gets trapped beneath the surface and accumulates inside a sac-like pocket. Most body cysts are benign, slow-growing, and caused by something mundane: a blocked pore, a minor injury, or the normal wear and tear on a joint. If you’ve noticed one or more lumps appearing on your skin, scalp, or near a joint, the cause usually falls into a handful of well-understood categories, though the specific type of cyst matters for knowing what to do about it.
The Most Common Skin Cysts
The overwhelming majority of cysts people notice on their body are either epidermoid cysts or pilar cysts. Both are benign, and both grow slowly enough that you might not even notice one until it’s been around for months.
Epidermoid cysts are the most frequently diagnosed type. They develop when skin cells that normally shed from the surface instead burrow deeper and multiply, forming a walled-off pocket filled with a thick, cheese-like material made mostly of keratin. They tend to show up on the face, neck, chest, and upper back, and they often have a small dark dot at the center, which is the plugged opening of a hair follicle.1Europe PMC. Overview of epidermoid cyst These aren’t caused by poor hygiene. A follicle can become blocked for no obvious reason, or after a minor scrape, a bug bite, or even a piercing that damages the skin just enough to redirect cells inward.
Pilar cysts are a close relative, but they originate from a slightly different structure in the hair follicle and are especially common on the scalp. They’re more common in women and form when keratin builds up inside a skin pore, blocking the exit of the oil gland’s secretions.2Europe PMC. Pilar Cysts of the Head and Neck: A Case Report If you’ve ever run your fingers through your hair and found a firm, round bump that rolls freely under the skin, that’s the classic feel of a pilar cyst. They’re painless unless they get inflamed, and they carry a very low risk of becoming anything dangerous.
Why Some People Get More Cysts Than Others
If you keep developing cysts, you’re not imagining a pattern. Some people are genuinely more prone to them, and the reasons range from skin type to genetics to hormonal shifts.
People with oilier skin or a history of acne tend to have more blocked follicles, which means more opportunities for cyst material to accumulate. Repeated friction from clothing, backpack straps, or shaving can also irritate follicles enough to set the process in motion. Hormonal changes during puberty, pregnancy, or polycystic ovary conditions can ramp up oil production and make cysts more likely in areas dense with oil glands.
There’s also a genetic component that goes beyond garden-variety skin tendencies. Steatocystoma multiplex, for example, is a condition where people develop dozens or even hundreds of small cysts, usually starting in adolescence. Researchers have traced this to mutations in a specific keratin gene (KRT17), and the pattern runs clearly through families: in one studied family, all ten affected members carried the same mutation, while none of the unaffected relatives did.3PubMed Central. Steatocystoma multiplex is associated with the R94C mutation in the KRTl7 gene If your parent had a lot of cysts, there’s a real chance you inherited the same tendency.
Gardner’s syndrome, a rare inherited condition linked to intestinal polyps and colon cancer risk, also includes epidermoid cysts as one of its visible features. A study investigating families with this syndrome found that the skin cysts were specifically epidermoid rather than other types, and they could be single or multiple.4PubMed. Epidermoid cysts, polyposis coli and Gardner’s syndrome If you’re developing multiple epidermoid cysts along with other unusual growths, a doctor may want to screen for underlying conditions like this.
Cystic Acne and Hidradenitis Suppurativa
Not every “cyst” that pops up on your body is a true cyst in the medical sense. Two common conditions produce painful, cyst-like lumps that people understandably call cysts, and both are worth understanding because they behave quite differently.
Cystic acne forms deep, inflamed nodules under the skin, usually on the face, chest, or back. These aren’t walled-off sacs like an epidermoid cyst; they’re severe inflammatory reactions within a pore. They tend to be more painful, redder, and more likely to scar. Steroid injections directly into the lesion can significantly reduce the size and severity of these nodules.5Dermatological Reviews. Steroid Injection Treatment for Nodulocystic Acne: A Literature Review If your “cysts” are appearing in acne-prone areas and are tender and inflamed from the start, you’re likely dealing with this rather than with true cysts.
Hidradenitis suppurativa (HS) is a chronic skin condition that causes recurring, painful lumps in skin folds: the armpits, groin, under the breasts, and around the buttocks. These lumps look and feel a lot like abscesses or boils, and they can drain foul-smelling fluid or form tunnel-like tracts under the skin. HS is frequently misdiagnosed at first because individual flares resemble ordinary infected cysts. Doctors should be suspicious of HS when a patient keeps getting what seem like skin abscesses in the same fold areas.6PubMed Central. What is hidradenitis suppurativa? If you’ve been treated repeatedly for “infected cysts” in your armpits or groin and they keep coming back, HS is worth discussing with a dermatologist. It’s not caused by infection or poor hygiene; it’s a chronic inflammatory process, and the treatment approach is fundamentally different from draining a one-off cyst.
Ganglion Cysts and Baker’s Cysts
Cysts don’t only affect the skin. Two common types develop around joints and tendons, and they can show up without any clear injury.
Ganglion cysts are the classic “Bible bumps” (so named because people used to smash them with a heavy book). They usually appear on the wrist, though they can form near any joint or tendon sheath. The cyst is filled with a thick, jelly-like fluid, and while the exact mechanism isn’t fully understood, the leading theory is that small droplets of a mucus-like substance leak from the joint lining and coalesce into a larger mass.7PubMed Central. Ganglion cysts of the wrist: pathophysiology, clinical picture, and management They can fluctuate in size, sometimes disappearing on their own and then returning. They’re harmless unless they press on a nerve and cause pain or tingling.
Baker’s cysts (also called popliteal cysts) form behind the knee. They’re essentially a swelling of the bursa, a fluid-filled cushion at the back of the joint, and they’re strongly associated with problems inside the knee itself. One study documented that Baker’s cysts consistently appeared alongside internal knee issues like meniscal tears, cartilage damage, or inflamed joint lining.8PubMed. Selected cases of arthroscopic treatment of popliteal cyst with associated intra-articular knee disorders primary report Even a partial meniscal tear, not necessarily a complete one, can be enough to trigger cyst formation.9PubMed. The frequency of Baker’s cysts associated with meniscal tears In people with knee osteoarthritis, Baker’s cysts add to the burden of symptoms and are associated with lower functional scores.10PubMed Central. Baker’s Cyst with Knee Osteoarthritis: Clinical and Therapeutic Implications If you have a Baker’s cyst, draining or removing it without addressing the underlying knee problem usually means it will come back.
When a Cyst Is Actually Something Else
One of the most common reasons people worry about cysts is that they aren’t entirely sure the lump they’re feeling is a cyst at all. Two other growths mimic cysts closely enough to cause confusion.
Lipomas are soft, rubbery lumps made of fat cells sitting just under the skin. They’re harmless and extremely common. The main differences: lipomas tend to feel softer and more “doughy” than cysts, they don’t have a central punctum, and they sit a bit deeper in the tissue. Ultrasound can reliably distinguish between the two. On imaging, lipomas show up as elongated masses with a striped pattern from internal dividers, while epidermoid cysts appear as round masses that partially indent into the skin layer above them.11Archives of Dermatology. Efficacy of Diagnostic Ultrasonography of Lipomas, Epidermal Cysts, and Ganglions If you have a lump and you’re not sure what it is, a quick ultrasound can settle the question without any cutting.
Abscesses are another common look-alike. An abscess is a pocket of pus caused by infection, and it tends to be red, hot, and painful. It develops quickly, often over days rather than the months or years a true cyst takes to grow. Sometimes a pre-existing cyst becomes infected and turns into an abscess, which is why the two get conflated. The treatment is different: an abscess needs draining and often antibiotics, while a quiet cyst may not need treatment at all.
What Happens If You Leave a Cyst Alone
Most skin cysts are perfectly fine left untouched. They don’t turn cancerous in any meaningful timeframe, and many people carry them for decades without trouble. Small cysts that aren’t causing symptoms can be safely ignored.12Journal of Medical Insight. Sebaceous cyst excision
The main risk with leaving a cyst is rupture. If the cyst wall breaks, either from trauma, squeezing, or just random bad luck, the keratin contents spill into the surrounding tissue and trigger a strong inflammatory reaction. This can be quite painful and produce significant swelling, redness, and tenderness, sometimes mimicking an abscess.13International Journal of Medical Science and Clinical Research Studies. Resection of a Ruptured Epidermoid Cyst with Limberg Flap: Case Report A ruptured cyst isn’t an emergency, but it usually sends people to the doctor faster than the original cyst ever did.
Malignant transformation, the thing many people quietly fear, is extremely rare. There are case reports of long-standing epidermoid cysts eventually developing into squamous cell carcinoma, but the mechanism isn’t well understood. The leading speculation is that prolonged chronic inflammation in a cyst that has been present for many years can, in rare cases, promote cellular changes that lead toward malignancy.14PubMed Central. A Rare Transformation of Epidermoid Cyst into Squamous Cell Carcinoma: A Case Report with Literature Review Repeated trauma, chronic infection, and cycles of injury and repair within the cyst have also been proposed as contributing factors, though the evidence supporting any single theory remains thin.15Medical Reports. A rare twist: Malignant transformation of epidermal cysts in the submandibular gland- A case report and literature review This is one of those risks that is real enough to know about but rare enough that it shouldn’t drive anxious decision-making about an ordinary cyst.
When Removal Makes Sense
The decision to remove a cyst usually comes down to whether it’s bothering you, not whether it’s medically necessary. Larger cysts that are cosmetically annoying, cysts in locations where they catch on clothing or get bumped frequently, and cysts that have become inflamed or ruptured in the past are all reasonable candidates for removal.
Complete excision, meaning the entire cyst wall is removed along with its contents, is the standard approach and the one most likely to prevent recurrence.12Journal of Medical Insight. Sebaceous cyst excision If a doctor simply drains the cyst by puncturing it and squeezing out the contents without removing the wall, the cyst will almost certainly refill. This is also why squeezing a cyst at home is generally counterproductive: you might push some material out through the surface, but you can also rupture the wall inward, trigger inflammation, and make the eventual surgical removal more difficult.
For ganglion cysts, the approach depends on symptoms. Many resolve without treatment. If the cyst is pressing on a nerve or limiting wrist motion, a doctor can aspirate the fluid with a needle, though recurrence rates after aspiration are fairly high. Surgical excision has a lower recurrence rate. Baker’s cysts behind the knee are best addressed by treating the underlying joint problem, since the cyst is usually a downstream effect of whatever is going wrong inside the knee.
Cysts That Form Inside the Body
The cysts most people worry about are the ones they can see or feel, but cysts also form internally, and these have very different causes and implications.
Ovarian cysts are extremely common in women of reproductive age. Most are functional, meaning they’re a normal byproduct of the ovulation cycle and resolve on their own within a few months. Some types, like endometriomas or dermoid cysts, are more persistent and may need monitoring or surgical removal.
Kidney cysts come in two broad flavors. Simple kidney cysts are common as people age and are almost always harmless. Polycystic kidney disease (PKD) is a different story entirely. It’s a genetic disorder in which multiple cysts progressively enlarge within both kidneys, crowding out normal tissue, accumulating fluid, and eventually impairing kidney function.16Polycystic Kidney Disease. Pathogenesis of polycystic kidney disease: basement membrane and extracellular matrix PKD runs in families and is one of the more common genetic causes of kidney failure. If you’ve been told you have multiple kidney cysts and you have a family history of kidney disease, PKD screening is worth pursuing.
In parts of the world where livestock farming is common and food hygiene standards vary, parasitic cysts caused by Echinococcus tapeworms can develop internally, especially in the liver and lungs.17PubMed Central. Echinococcus Granulosus, a Parasite Producing Hydatid Cyst: A Review These hydatid cysts can grow quite large and cause symptoms depending on their location and size.18PubMed Central. Hydatid Cyst or Echinococcosis: A Comprehensive Review of Transmission, Clinical Manifestations, Diagnosis, and Multidisciplinary Treatment This is uncommon in urban settings in high-income countries, but if you’ve lived or traveled in endemic regions and develop unexplained internal cysts, it’s a cause your doctor should consider.
Practical Signals Worth Paying Attention To
Most cysts are unremarkable, but a few patterns warrant a trip to the doctor sooner rather than later:
- Rapid growth: A cyst that has been stable for years and suddenly starts growing quickly deserves evaluation, because it could indicate inflammation, infection, or (very rarely) something more concerning.
- Pain or redness: Cysts are normally painless. If one becomes tender, red, or warm, it may be inflamed or infected.
- Recurring lumps in skin folds: Multiple episodes of painful bumps in the armpits, groin, or under the breasts suggest hidradenitis suppurativa rather than isolated cysts, and the treatment approach differs substantially.
- Multiple cysts developing at once: A sudden crop of cysts in a young adult could indicate a genetic condition like steatocystoma multiplex. Multiple epidermoid cysts alongside digestive symptoms may warrant investigation for Gardner’s syndrome.
- Cysts in unusual locations: A lump behind the knee in someone with knee pain or stiffness is likely a Baker’s cyst and signals something happening inside the joint that should be evaluated.
The vast majority of people asking “why am I getting cysts?” are dealing with ordinary epidermoid or pilar cysts driven by blocked follicles, skin type, and genetics. These are as routine as moles or skin tags. But paying attention to the pattern, including where the cysts form, how many appear, how fast they grow, and whether they recur after treatment, gives you and your doctor the information needed to tell a boring cyst story from one that deserves closer attention.