An infected cyst typically appears as a swollen, red, tender lump that’s noticeably larger and more painful than it was before. The skin over and around it often looks discolored, feels warm to the touch, and may ooze thick, foul-smelling fluid. Recognizing these changes early matters, because an infected cyst can worsen quickly if left alone.
How an Infected Cyst Looks and Feels
Most skin cysts sit quietly under the skin for months or years as small, painless bumps. When one becomes infected, the change is usually obvious. The area turns red or darker than the surrounding skin, swells significantly, and becomes tender or outright painful even without touching it. The skin over the cyst may look stretched and shiny from the pressure building underneath.
In the early stages of infection, the lump feels firm and hard. As pus collects inside, the center gradually softens and the overlying skin thins out. At this point, you might notice the cyst feels squishy or fluid-filled when pressed gently. The area around it often radiates warmth you can feel with the back of your hand.
Pain can range from a dull ache to a sharp, throbbing sensation, especially if the cyst is pressing on nearby nerves. The discomfort tends to worsen over two to four days as the infection progresses.
What the Discharge Looks Like
If an infected cyst ruptures or begins to drain on its own, you’ll likely see thick, milky fluid that can range in color from white or yellow to green, pink, or brown. The smell is often distinctly unpleasant. This discharge is pus, a mix of dead white blood cells, bacteria, and tissue debris your body produces while fighting infection.
A ruptured cyst that was already infected can quickly develop into a boil-like wound that needs prompt treatment. The drainage itself isn’t necessarily a sign things are getting better. Without proper care, a draining cyst can continue to harbor bacteria and reinfect.
Infected Cyst vs. MRSA Boil
An infected cyst and a staph-related boil (including MRSA) can look strikingly similar in the early stages. Both start as a red, painful lump that fills with pus. A few differences can help you tell them apart, though neither should be diagnosed at home.
- Speed of onset: MRSA boils often start as something that looks like a pimple or small bug bite, then rapidly turn into a hard, painful red lump over just a day or two. An infected cyst usually develops more gradually on top of a bump you already knew was there.
- Pain level: MRSA infections tend to hurt significantly more than seems proportional to the size of the lesion. If a small skin bump is causing intense pain, that’s a red flag.
- Clustering: MRSA can produce a cluster of pus-filled blisters, while an infected cyst is typically a single lump.
- Fever: A fever alongside an unusually painful skin lesion is more suggestive of a bacterial infection like MRSA and warrants urgent evaluation.
Signs the Infection Is Spreading
Most infected cysts stay localized, but bacteria can occasionally spread into surrounding tissue or the bloodstream. The clearest warning sign is red streaks extending outward from the cyst toward your armpit or groin. These streaks, which may be faint or vivid, indicate the infection has reached your lymphatic system. This is a condition called lymphangitis, and it can become life-threatening if bacteria enter the blood.
Other signs of a worsening infection include increasing redness that expands well beyond the cyst itself, swelling that keeps growing after three to four days, and fever or chills. Any of these warrant same-day medical attention.
Why You Shouldn’t Squeeze or Pop It
It’s tempting to try to drain an infected cyst yourself, but squeezing it pushes bacteria deeper into surrounding tissue. This can turn a contained infection into a spreading one, potentially causing a deeper soft-tissue infection. A ruptured cyst also creates an open wound that’s vulnerable to reinfection.
There’s a practical reason to leave it alone, too. An inflamed cyst is much harder for a doctor to fully remove. If you aggravate it, your provider will likely need to wait for the inflammation to calm down before they can do a complete excision, which means a longer process overall and a higher chance the cyst comes back.
What Treatment Looks Like
For a small infected cyst that hasn’t formed a large abscess, your doctor may prescribe oral antibiotics. Treatment typically lasts about five days, though courses can extend up to 14 days for severe infections, slow-healing wounds, or people with weakened immune systems.
If the cyst has developed into a sizable abscess with a pocket of pus, it usually needs to be drained in a clinical setting. This involves numbing the area and making a small incision to let the pus escape. The relief is often immediate because the built-up pressure is what causes most of the pain. After drainage, the wound is sometimes packed with sterile gauze that you’ll need to change at home over the following days.
Once the infection is fully resolved and the inflammation has settled, your doctor may recommend removing the cyst wall entirely. Without complete removal, cysts frequently refill and can become infected again. A cold compress applied to the area in the meantime can help manage pain and reduce swelling while you wait for treatment or for antibiotics to take effect.