What Is Cellulitis: Symptoms, Causes, Diagnosis, Treatment, and Prevention
Cellulitis is a potentially dangerous bacterial infection that affects the deeper layers of the skin, including the dermis, or second layer of skin, and the subcutaneous tissue, or fat and connective tissue that form the bottom layer of skin. (The top layer of skin is called the epidermis.)
“Cellulitis literally refers to inflammation of the skin,” says Tsippora Shainhouse, MD, a board-certified dermatologist and founder of SkinSafe Dermatology and Skin Care in Los Angeles.
“It usually appears in the skin as an expanding pink or red patch that feels warm and hard and sometimes tender to touch,” says Dr. Shainhouse.
Cellulitis can start with any break in the skin, including a minor scratch or insect bite, that allows bacteria to penetrate to the deeper layers of skin. It’s rare in healthy young adults. Cellulitis is more common among elderly people and in people with weakened immune systems, chronic skin conditions that cause breaks in the skin, chronically high blood sugar levels, or obesity.
Systemic antibiotics — oral antibiotics or, in severe cases, intravenous antibiotics — are needed to treat cellulitis. Because cellulitis affects the deeper layers of skin and tissue, topical antibiotic ointments are not effective at treating cellulitis.
Cellulitis that goes untreated can spread to the lymph nodes and the bloodstream and quickly become life-threatening.
Given the serious nature of cellulitis, it’s important to seek medical care if you develop symptoms of the condition — even if you’re not sure that’s what you have.
As mentioned previously, cellulitis most often occurs in the legs in adults and, according to Shainhouse, it typically occurs in one leg at a time, not both at once.
Common symptoms of cellulitis include:
“In more severe cases, additional clinical features may include blister formation, pustules (bumps on the skin containing pus), and necrosis (skin breakdown),” Shainhouse says.
Cellulitis usually doesn’t go away on its own.
“Cellulitis is usually caused by a variety of bacteria, most predominantly staphylococcal and streptococcal species that live on the skin. These bacteria invade below the skin through abrasions and cuts and infect the tissues beneath the skin, causing an inflammatory response,” says Amesh A. Adalja, MD, an infectious disease physician in Pittsburgh and a senior scholar at the Johns Hopkins University Center for Health Security.
While staphylococcal and streptococcal bacteria can live harmlessly on your intact skin, any type of open sore on your body — including a burn, a surgical wound, or even a pimple — can allow the bacteria in and put you at risk of developing cellulitis, says Shainhouse.
Of course, many people sustain many minor skin wounds over the course of their lives and never develop cellulitis. But certain conditions place people at increased risk for cellulitis. Such conditions include:
There’s also the risk of cellulitis if you have a skin condition like eczema or athlete’s foot that can cause dryness and itchiness and breaks in the skin, providing an entry point for bacteria.
“Some common mimickers of cellulitis include venous stasis dermatitis, contact dermatitis, eczema, an insect bite reaction, shingles, deep vein thrombosis (DVT), vein inflammation, and gout,” says Shainhouse.
It’s also important to rule out necrotizing fasciitis, a bacterial infection that can quickly destroy the tissue beneath the layers of skin. This is the condition commonly referred to as “flesh-eating disease.”
Venous Stasis Dermatitis This type of redness and swelling of the lower legs is due to poor blood circulation. It usually affects both legs at once and is associated with rough, scaly skin and itchiness.
Contact Dermatitis Allergic contact dermatitis occurs when the skin comes into contact with an allergen, such as certain metals or poison ivy. The skin can become red, swollen, and blistered, but this type of reaction doesn’t usually cause a fever. Oftentimes the rash of contact dermatitis will form the shape of the allergen — for example, a rash that circles the wrist suggests that a watchband may be to blame, or a rash in a straight line across the ankle mimics the path of the poison ivy leaf that brushed against the skin.
Eczema Atopic dermatitis, or eczema, tends to cause itching, red or scaly skin, and, sometimes, raised bumps that leak and crust over. It can occur anywhere on the body and does not favor the legs.
Shingles Caused by the virus that causes chickenpox, shingles causes a painful rash that usually appears as a row of blisters. It can occur anywhere on the body but is usually limited to one side at a time.
Tinea Pedis Also known as athlete’s foot, this common fungal infection typically causes redness, itchiness, scaly skin, and, sometimes, blisters and cracking of the skin on the feet.
Gout Gout occurs when uric acid crystals form in a joint, causing pain, swelling, and stiffness. Gout can also cause the skin over the affected joint to appear red and feel warm to the touch.
Deep Vein Thrombosis A blood clot, or thrombosis, in a deep vein of the leg can cause swelling, pain, and warmth. Like cellulitis, deep vein thrombosis usually happens in only one leg at a time. You should seek medical help if you have signs or symptoms of deep vein thrombosis.
Vein Inflammation Known as phlebitis, inflammation in a vein can cause pain, swelling, redness, and warmth. Phlebitis can be caused by deep vein thrombosis and also by varicose veins. You should seek medical attention if you develop symptoms of phlebitis.
Lipodermatosclerosis Lipodermatosclerosis refers to changes in the skin of the lower legs caused by inflammation of the layer of fat underneath the skin. The skin may become reddish and harder and darker in color than usual. The leg itself may become swollen, and the condition can be painful. One or both legs may be affected. You should seek medical help if you have signs or symptoms of lipodermatosclerosis.
“When symptoms progress quickly or become severe, go to the emergency room,” advises Shainhouse.
Treatment of cellulitis depends on the severity of the condition. In most instances, an oral antibiotic should take care of the infection. But some cases may require intravenous antibiotics administered in a hospital setting.
If you develop cellulitis again, after starting maintenance therapy, your doctor may need to conduct further testing to determine the cause of your infection, or you may be referred to an infectious disease specialist.
One of the best strategies for preventing cellulitis is to practice proper first aid when you have a skin injury.
For a minor cut or scratch, that generally means cleaning and covering the wound yourself or with the help of a companion.
Soaking the wound with diluted white vinegar can also kill more than 20 types of harmful bacteria present in wounds. Mix three parts water to one part white vinegar. Soak the wound or apply gauze saturated with the vinegar for 10 minutes.
People with diabetes, in particular, “should take meticulous care of their feet and be aggressive with treating even minor skin issues,” says Dr. Adalja. “Athlete’s foot (fungal infections on the feet) can cause skin to be more prone to bacterial infection, so this should be treated promptly. Also, they should receive routine podiatric care.”
If you have diabetes, examine your feet daily for redness, areas of warmth, signs of pressure or rubbing from shoes, blisters, or injuries of any type. Apply moisturizer to your feet to prevent cracking, but avoid putting moisturizer in the areas between your toes. In addition, keep your toenails and fingernails trimmed to prevent injury from scratching.
Addressing the underlying risk factors for cellulitis can also help to prevent it. Such measures might include:
Even with the best first aid, infections can still occur. In this case, early detection is key to avoiding serious complications. Signs of an infected wound include:
Untreated cellulitis can lead to some serious medical conditions, including:
Another major complication is the infection spreading to your bloodstream, at which point the infection becomes life-threatening.
You can raise your chances of heading off complications by doing the following:
Here’s what researchers have learned about cellulitis:
As noted above, the staphylococcal and streptococcal bacteria that usually cause cellulitis can contribute to other problems, too.
In addition to openings in the skin, staph bacteria can enter the body via urinary catheters, intravenous lines (or other implanted medical devices), and unsanitary needles.
Both staph and strep bacteria can cause impetigo, a highly contagious skin condition that causes crusty, red sores, usually on the face, arms, and legs. It usually affects children more than adults, and though it may look worrisome, it’s generally harmless when properly treated with antibiotics.
Cellulitis is a serious bacterial skin infection that can quickly develop from a minor scratch or bite. If left untreated, it can spread to the lymph nodes and bloodstream, becoming life-threatening. Always seek medical care if you have skin that is red, swollen, warm, and possibly accompanied by fever. Your best line of defense is cleaning and properly caring for any cuts or wounds to stave off infection.
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