An infected cyst typically shows a combination of increasing pain, swelling, redness or skin discoloration, warmth to the touch, and discharge that may be yellow, green, or foul-smelling. These signs develop over days and tend to worsen rather than plateau, which is the clearest distinction from a cyst that’s simply irritated or inflamed.
Inflamed vs. Infected: Key Differences
Not every swollen, painful cyst is infected. Cysts can become inflamed from friction, pressure, or minor irritation without any bacteria being involved. An inflamed cyst is swollen and tender, but the skin around it generally looks normal or only mildly pink. The swelling stays contained, and there’s no discharge.
An infected cyst looks and feels different. Your body is actively fighting bacteria inside the cyst, which causes more intense swelling, sharper pain, noticeable skin discoloration (deepening redness or darkening depending on your skin tone), and warmth radiating from the area. The skin over the cyst may appear tight and shiny. If the cyst ruptures, it often leaks a thick, cheesy, foul-smelling substance. That material is keratin, a protein that normally fills these cysts, but when bacteria are present, the drainage can turn yellow or greenish and smell noticeably worse than a sterile rupture would.
The simplest way to gauge the difference: an inflamed cyst is uncomfortable. An infected cyst gets worse each day, hurts without being touched, and develops visible changes in the surrounding skin.
What Causes a Cyst to Get Infected
Most cyst infections happen when bacteria enter through a small break in the skin overlying the cyst. This can occur from squeezing or picking at the cyst, shaving over it, or even just from friction against clothing. The most common culprit is Staphylococcus aureus, the same bacterium responsible for most skin abscesses. In some cases, the infection involves MRSA, a strain resistant to several common antibiotics, which has become increasingly common in skin infections.
Certain factors raise your risk. Any break in the skin nearby, whether from a cut, scrape, or dry cracked skin, gives bacteria a way in. A weakened immune system, excess body weight, and a history of previous skin infections all increase the likelihood that a cyst will become infected rather than simply staying dormant.
Signs the Infection Is Spreading
A localized cyst infection, while painful, is usually manageable. The concern is when bacteria move beyond the cyst into the surrounding tissue or bloodstream. Cellulitis, a spreading skin infection, develops when bacteria push into deeper tissue layers. You’ll notice the redness expanding outward from the cyst rather than staying contained around its border. The affected area may feel hot, firm, and increasingly painful over hours rather than days.
Red streaks radiating outward from the cyst are a particularly urgent sign. These streaks indicate lymphangitis, an infection of the lymphatic vessels that can move fast. In less than 24 hours, an infection can spread from the initial site to other areas of the lymphatic system and potentially enter the bloodstream.
Systemic symptoms mean the infection has gone beyond the skin. Watch for:
- Fever or chills, especially if they come on suddenly
- Rapid heart rate or fast breathing that feels out of proportion
- Confusion or unusual fatigue
- Warm, clammy, or sweaty skin beyond the immediate cyst area
These are signs of a potentially serious response to infection. A high heart rate, confusion, or rapid breathing can be early indicators that the body is struggling to contain the bacteria. Left untreated, a spreading skin infection can progress to sepsis, a life-threatening condition where the body’s response to infection starts damaging its own organs.
Why You Shouldn’t Squeeze or Drain It Yourself
Squeezing an infected cyst forces bacteria deeper into surrounding tissue and can push the infection from a contained pocket into an open wound. It also increases the risk of scarring. Even if the cyst looks like it’s ready to drain, breaking the skin yourself introduces new bacteria and creates a larger entry point for infection.
If a cyst ruptures on its own, keep the area clean and place a warm, moist cloth over it to encourage complete drainage and healing. Don’t try to press out remaining material.
What Treatment Looks Like
The standard treatment for an infected cyst that has formed an abscess is incision and drainage, a procedure where a healthcare provider opens the cyst, removes the infected material, and cleans the cavity. This is usually done in an office visit or emergency department and takes only a few minutes under local anesthesia. The area is then packed with gauze or left open to continue draining.
One important detail many people don’t realize: antibiotics alone, without drainage, are ineffective at treating an abscess. The walled-off pocket of infection prevents antibiotics from reaching the bacteria inside. Antibiotics may be prescribed alongside drainage, particularly if there’s surrounding cellulitis or concern about MRSA, but they aren’t a substitute for removing the infected material. Very large abscesses or those in difficult-to-numb locations may need to be handled in an operating room by a surgeon.
After drainage, most cysts heal over one to three weeks with regular dressing changes. The cyst wall itself is often left in place during an acute infection and can be removed later in a separate procedure once the inflammation has resolved. Without removing the cyst wall entirely, there’s a chance the cyst will refill over time.