Cellulitis: A Rash That Needs Treatment
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What is cellulitis?
Cellulitis is a bacterial infection of the skin and the soft tissue beneath the skin. Cellulitis usually occurs when bacteria enter the skin through small cuts or scrapes. It can happen anywhere on the body but most commonly affects the legs.
Cellulitis creates a red, swollen rash with no real borders. It may be warm and painful. Cellulitis can also make you feel sick, causing a fever, fatigue, and other changes like a fast heart rate. It needs to be treated with antibiotics, and takes a few days to a week to heal.
Be sure to let your doctor know if you have significant pain, fever, malaise, or other systemic symptoms. Or if your skin blisters or turns black. —Dr. Mollie MacCormack
Cellulitis often looks like a red or purplish area of the skin. You may notice a small cut or wound in the area, but not always. This may have been where the bacteria entered the skin. The area of cellulitis will probably feel hot to the touch and painful. It may also feel firm or swollen. Sometimes, blisters form on the surface.
With more serious cases, you may also have bodywide symptoms, like a fever, chills, muscle aches, tender and enlarged lymph nodes, rapid heart rate, fast breathing, low blood pressure, and overall weakness.
There are other inflammatory and infectious skin conditions that may seem similar to cellulitis. For example, deep venous thrombosis, lyme disease, insect bites, drug reactions, contact dermatitis, among others. Cellulitis is more likely to be red, hot, firm, and painful with poorly defined borders.
- Ill-defined borders
- Hot to the touch
- Firm or swollen compared to surrounding area
- Blisters or bruising
- Fevers, chills, fast heart rate, generally feeling bad (malaise)
- Enlarged lymph nodes
- Occurs on one side of the body
- Most commonly involves the leg
Other symptoms you may have
Left untreated, cellulitis can progress and turn into a very serious condition. More severe infections, such as necrotizing fasciitis, gas gangrene, and toxic shock syndrome, can also be confused with cellulitis in their early stages.
Go to the emergency department if you develop any of the following symptoms:
- Crackling sensation felt under the infected skin
- Dark brown discharge from a wound
- Extreme pain
- No pain, and instead numbness
- Purplish-grey skin color
Causes of cellulitis
Bacteria live on the surface of our skin. Normally, it doesn’t cause any harm. But when you get a cut, bite, needle puncture, or some other kind of abrasion, bacteria can get into the deeper layers of skin and cause infection.
Many different types of bacteria can cause cellulitis. The most common types are:
- Group A Streptococcus: This is the bacteria that causes strep throat. It’s also the most common cause of cellulitis.
- Staphylococcus Aureus (Staph): This is the second most common cause.
- Methycillin Resistant Staphylococcus Aureus (MRSA): This is a group of staph bacteria that is resistant to many antibiotics. Cellulitis from MRSA is harder to treat.
- Pseudomonas: This is more likely to affect diabetics and those in hospitals.
There’s a more superficial type of cellulitis, called erysipelas, that affects the upper layer of the dermis (below the outer layer of skin) and tends to occur on the legs and face. It is more likely to have bodywide symptoms early on, the redness is more intense and more sharply defined, and it can progress rapidly.
Ask your doctor: What should I do if my infection is spreading or becoming increasingly painful? —Dr. MacCormack
A doctor will take your medical history and do a physical exam. They may mark the area that is red, so they can monitor its progression. Tests that may be ordered include blood tests, testing the fluid in your skin, or a skin biopsy (if they are uncertain about the diagnosis).
Cellulitis is treated with oral antibiotics. However, you may have to be hospitalized and given antibiotics through an intravenous (IV) line if you are very sick, have a compromised immune system, have had antibiotics and are not responding, or the cellulitis involves the face (especially around the eye).
Though antibiotics normally start working within a few days, it’s important to finish all of them to make sure the infection is completely gone.
Risk factors for cellulitis
Tinea pedis (Athlete’s foot) may predispose you to developing cellulitis due to breakdown of skin between the toes. —Dr. MacCormack
Cellulitis is most likely to occur after trauma to the skin. This includes a cut or scrape, an insect or animal bite, having an IV or medical device placement, or incisions to the skin during surgery. Skin between the toes that is white and wrinkly (macerated), typically caused by tinea pedis (athlete’s foot), can also allow bacteria to enter the skin.
A weakened immune system also increases the risk of cellulitis. This includes people with immunosuppressive diseases (like diabetes, cancer, or AIDS) or those on immunosuppressive medications.
Also, conditions that affect blood flow to your arms or legs—like peripheral artery disease, venous insufficiency, deep vein thrombosis, and previous vein harvesting—may keep wounds from healing properly. This increases your chances of getting cellulitis, especially in the legs.
If you think you have cellulitis, see your primary care doctor right away or go to urgent care or the emergency department.
If you are having fevers, chills, changes in heart rate, or malaise, go straight to the emergency room. The infection is treatable, but should be started as soon as possible. This is especially urgent for people with diabetes, compromised immune systems, vascular disease, or other high risk conditions. If left untreated, cellulitis can become dangerous and can result in the loss of a limb or even be fatal.
As soon as you notice the rash, outline it with a permanent marker. It will help the doctor know if and how fast it is spreading.
Since cellulitis is from bacteria entering the skin, it’s important to thoroughly clean and bandage all cuts and abrasions. Keep any openings in the skin clean, dry, and covered.
Good hand hygiene also helps prevent cellulitis. Keep hands clean by washing with soap and water regularly.
Treating diseases that make you more likely to get cellulitis, like diabetes and peripheral artery disease, is important. People with these diseases should also practice excellent foot hygiene to minimize risk of skin injury. They should also try to reduce the chances of getting a cut on their feet in the first place, by wearing shoes and socks.
William C. Fix is a resident physician specializing in dermatology at the Albert Einstein College of Medicine and Montefiore Medical Center in New York. He graduated from Brown University with a BA in Economics in 2012 and obtained his MD from the University of Pennsylvania Perelman School of Medicine in 2019. William has received grants from the American Society for Dermatologic Surgery, The National Institutes of Health and the Alex’s Lemonade Stand Foundation for oncology research, and was selected for the University of Pennsylvania’s Dermatology Oncology Center (PennDOC) Research Fellowship in Dermatology & Dermatologic Surgery. William’s interests include general and procedural dermatology, cutaneous oncology, technology, and quality improvement.