Common Skin Infections: Cellulitis, Erysipelas, Impetigo Diagnosis

  • Diagnosis

    There are three common types of skin infections: cellulitis, erysipelas, and impetigo (pyoderma).

    Cellulitis is usually an easily treated, but potentially dangerous skin infection. Cellulitis sometimes results when a cut, scrape, insect bite, splinter, or other break in the skin allows bacteria to enter underlying tissues. While a scrape or a cut will not usually result in cellulitis, a tender, firm, painful, and rapidly expanding area of redness on the skin surrounding broken skin should be a cause for concern. Often, lymph nodes close to the affected skin will be enlarged, and there may be red streaks running through the skin away from the infection.

    Erysipelas is a form of cellulitis that affects only the top layers of the skin. It is more common among children and the elderly. Erysipelas differs from cellulitis in that the inflamed area is distinct from surrounding skin—it is raised, firm, and the redness is sharply marked off. Erysipelas is often found on the face; however, it can also develop on the arms and legs. Sometimes the skin will have what is called a 'peau d'orange,' or orange peel, look to it.

    Impetigo (pyoderma) is the most common bacterial infection of the skin. It is contagious and can happen at any age, but is most common in young children. Impetigo appears in the form of reddish sores that blister to produce a yellow-brown fluid. This fluid dries to form a thick, honey-colored crust. The sores are not usually painful, but can itch. They are usually found on exposed parts of the body like the hands, feet, and legs. Bullae, which look like blisters, may also be present, and spread rapidly. Bullous impetigo is most often found on the face, arms, and legs.

    Warm temperatures, humidity, poor hygiene, and crowded living conditions make the spread of impetigo easier. When the sores of impetigo are deep, causing larger ulcers, the infection is called ecthyma. As with cellulitis and erysipelas, impetigo is not difficult to treat, but requires the attention of a physician.

    The most common cause of cellulitis is a family of bacteria called Group A streptococcus, the same bacteria that cause strep throat. The streptococcus bacteria exist on the skin and in the throats of large numbers of people without any ill effects. However, when the bacteria penetrate the protective barrier of the skin, they can cause serious disease. Streptococci make proteins called enzymes that break down the skin and allow bacteria to spread. They also produce toxins that cause the body to start a protective response, leading to more inflammation.

    Another organism, called Staphylococcus aureus, also causes cellulitis, and is second in occurrence only to Group A streptococcus.

    In some cases, other, more rare types of bacteria cause cellulitis:

    • Steptococcus galactiae (Group B streptococcus) attacks those with impaired immune systems, the elderly, and people with diabetes.
    • Hemophilis influenzae can cause cellulitis in the skin surrounding the eye (periorbital cellulites) in children. These bacteria are often associated with sinus infection (sinusitis), ear infection (otitis media), or a serious infection of the throat called epiglottitis. Childhood vaccination for hemophilis has made this infection less common.
    • Pasteurella multocida is associated with dog and cat bites.
    • Pseudomonas aeruginosa can cause infection of a hair follicle after bathing in contaminated water (hot tub folliculitis), as well as cellulitis. Cellulitis may also occur after a person has stepped on a nail or had some other type of penetrating injury.
    • Erysipelothrix rhusiopathiae can cause cellulitis in people who work as meat workers, bone renderers, and fishmongers.
    • Vibrio vulnificus (and other Vibrio species) can enter the skin directly (usually from contaminated seawater) and cause cellulitis or, rarely, be ingested in the form of undercooked seafood. From the gut, Vibrio vulnificus can enter the bloodstream and “seed” the skin.

    Group A strep usually causes erysipelas. Other streptococcus types and rarely, staphylococcus, another type of bacteria, may be involved. Unlike many other organisms, streptococci have infrequently developed drug resistance. As a result, most of these infections, if treated early, do not require expensive new or broad-spectrum antibiotics. They can generally be treated with oral forms of penicillin, or agents like erythromycin for those allergic to penicillin.

    A mixture of streptococcus and staphylococcus usually causes impetigo. Because staphylococcus is almost universally resistant to basic penicillin, advanced penicillins or other types of oral antibiotics are used to treat this infection.

    Both cellulitis and erysipelas start and spread quickly, and cause redness, swelling, pain, and warmth. People who have one of these infections may feel worn out and sick, and have a fever. In severe cases of cellulitis, widespread symptoms of infection may appear, including fever, chills, low blood pressure, rapid breathing, and rapid heartbeat.

    The common form of impetigo begins with a small (2-4 mm/.04-.16 in) reddened, flat area of skin (macule) that rapidly forms either a clear or pus-filled blister (vesicle or pustule). These blisters are fragile and rupture easily, releasing a fluid that dries into a golden crust. The sores itch, and scratching them causes the infection to spread to other areas. The wounds take a while to heal, but do not leave permanent scars. In the bullous form of the disease, which is less common, the blisters are larger, tense, and filled with a clear fluid. People with this form of impetigo may also have a fever, diarrhea, and general weakness—symptoms not found in common impetigo.

    Skin infections accompanied by cell death (necrotizing infections) often cause pain, fever, malaise, and a dark swelling of the affected area. As the infection progresses, the skin will become darker, moving from deep red to blue or black—a signal that it has become gangrenous. Bullae, or large blisters filled with dark fluid, may appear. The infection spreads rapidly in underlying tissues, which is not apparent from the appearance of the overlying skin.

    Certain conditions that impair circulation or immunity predispose people to skin infections such as cellulitis. These conditions include:

    • Diabetes
    • Disease of the blood vessels in the arms or legs (arteries or veins) or conditions that worsen the circulation, such as heart failure
    • Age (the very young and the elderly are at greater risk)
    • Recent surgery or childbirth
    • Chronic skin conditions that cause breaks in the skin (i.e., eczema)
    • Intravenous (IV) drug abuse
    • Cirrhosis (advanced liver disease)
    • Obesity
    • HIV/AIDS
    • Systemic cancers, especially if treated with chemotherapy or radiation
    • Athlete's foot
    • Trauma

    Skin and soft-tissue infections such as cellulitis are more common among people whose immune systems are not working properly, such as those with cancer. An impaired immune system makes a person less able to fend off disease, and when infected, less capable of controlling an infection. For cellulitis, some of these immunosuppressed states might include diseases such as cancer, but also therapy for cancer or immunosuppression for transplant surgery.

    In addition, some diseases make the skin and underlying tissues more vulnerable to bacteria by slowing blood flow. Diabetes is in this category. Removal of the saphenous vein in the leg for bypass surgery also can cause swelling (edema) and poor blood flow. As a result, the skin may break open. Those who have had recent surgery or other trauma to tissues (such as childbirth or an accident) may expose normally sterile tissues to bacteria, making cellulitis more likely.

    Poor hygiene can increase the risk of impetigo.

    Your doctor will perform a physical examination of your skin. He or she will suspect cellulitis or erysipelas if you have a spreading, swollen, reddened, warm, and tender area of skin that developed rapidly. The area may surround a break in the skin, and you may feel ill and have chills or fever. The doctor will check for involvement of the face, which is common in erysipelas, and involvement of the legs, which is common in cellulitis. Cellulitis and erysipelas differ in that erysipelas tends to have a sharper border between affected and unaffected skin.

    In some cases, doctors will try to identify the specific bacteria causing the cellulitis by taking a specimen for culture. This is often done using a needle. Punch biopsy, which takes a sample of tissue, may also help differentiate cellulitis from some other similar-appearing skin disease. If a cut is present, it may be possible to get a sample of bacteria by swabbing the wound. Laboratory tests may or may not be ordered in suspected cases of cellulitis, as most findings tend not to be specific for this infection. Blood cultures are usually done for severely ill patients.

    Your doctor will suspect impetigo if you have a honey-colored crust covering a blistered rash.

    Your doctor may suspect a necrotizing infection if, in addition to skin symptoms similar to those of cellulitis, you have pain that is out of proportion to the apparent size of your infection.

    Low blood pressure, fast breathing, and a fast heart rate are signs of a more serious or advanced infection. In those who are suspected of having an advanced, or necrotizing cellulitis, doctors may order x-rays, a CT scan, or an MRI to better define the extent of infection. Surgery may also be necessary to cut into the infection and probe the underlying tissue in order to ensure that a serious infection is not present.

    It is important to control conditions that might make you more likely to have an outbreak of cellulitis. In particular, diabetes must be carefully controlled, and proper foot care is essential for those with this disease.

    If you have swelling (edema) of the legs or arms due to a heart condition or surgery, try to follow advice to reduce the edema, and take special care of your skin and be sure to report any changes in skin color or skin erosions to your doctor.

    If you have a splinter, cut, scrape, or insect bite, keep the wound clean and report any changes in the surrounding skin to your physician. Using antibiotics to prevent cellulitis is not recommended.

    See your physician if you have athlete’s foot or another fungal infection that does not improve.

  • Prevention and Screening

    It is important to control conditions that might make you more likely to have an outbreak of cellulitis. In particular, diabetes must be carefully controlled, and proper foot care is essential for those with this disease.

    If you have swelling (edema) of the legs or arms due to a heart condition or surgery, try to follow advice to reduce the edema, and take special care of your skin and be sure to report any changes in skin color or skin erosions to your doctor.

    If you have a splinter, cut, scrape, or insect bite, keep the wound clean and report any changes in the surrounding skin to your physician. Using antibiotics to prevent cellulitis is not recommended.

    See your physician if you have athlete’s foot or another fungal infection that does not improve.

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I'm Shereen A. Gharbia, PharmD. Welcome to PDR Health!

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Common Skin Infections: Cellulitis, Erysipelas, Impetigo Related Drugs

Common Skin Infections: Cellulitis, Erysipelas, Impetigo Related Conditions