A severe case of facial impetigo
|Classification and external resources|
|Specialty||Dermatology, infectious disease|
|eMedicine||derm/195 emerg/283 med/1163 ped/1172|
Impetigo is a bacterial infection that involves the superficial skin. The most common presentation is yellowish crust on the face, arms, or legs. Less commonly there may be large blisters which affect the groin or armpits. The lesions may be painful or itchy. Fever is uncommon.
It is typically due to either Staphylococcus aureus or Streptococcus pyogenes. Risk factors include attending daycare, crowding, poor nutrition, diabetes, contact sports, and breaks in the skin such as from mosquito bites, eczema, or scabies. With contact it can spread around or between people. Diagnosis is typically based on the symptoms.
Prevention is by handwashing, avoiding people who are infected, and cleaning injuries. Treatment is typically with antibiotic creams such as mupirocin or fusidic acid. Antibiotics by mouth, such as cephalexin, may be used if large areas are affected. Antibiotic resistant forms have been found.
Impetigo affected about 140 million people (2% of the population) in 2010. It is most common in young children but can occur at any age. Without treatment people typically get better within three weeks. Complications may include cellulitis or poststreptococcal glomerulonephritis. The name is from the Latin impetere meaning "attack".
Signs and symptoms
This most common form of impetigo, also called nonbullous impetigo, most often begins as a red sore near the nose or mouth which soon breaks, leaking pus or fluid, and forms a honey-colored scab, followed by a red mark which heals without leaving a scar. Sores are not painful, but they may be itchy. Lymph nodes in the affected area may be swollen, but fever is rare. Touching or scratching the sores may easily spread the infection to other parts of the body. Ulcerations with redness and scarring also may result from scratching or abrading of the skin.
Bullous impetigo, mainly seen in children younger than 2 years, involves painless, fluid-filled blisters, mostly on the arms, legs, and trunk, surrounded by red and itchy (but not sore) skin. The blisters may be large or small. After they break, they form yellow scabs.
In this form of impetigo, painful fluid- or pus-filled sores with redness of skin, usually on the arms and legs, become ulcers that penetrate deeper into the dermis. After they break open, they form hard, thick, gray-yellow scabs, which sometimes leave scars. Ecthyma may be accompanied by swollen lymph nodes in the affected area.
It is primarily caused by Staphylococcus aureus, and sometimes by Streptococcus pyogenes. Both bullous and nonbullous are primarily caused by S. aureus, with Streptococcus also commonly being involved in the nonbullous form.
Impetigo is more likely to infect children ages 2-6, especially those that attend school or daycare. Other factors can increase the risk of contracting impetigo such as diabetes, dermatitis, immunodeficiency disorders, and other irritable skin disorders.  Impetigo occurs more frequently among people who live in warm climates.
The infection is spread by direct contact with lesions or with nasal carriers. The incubation period is 1–3 days after exposure to Streptococcus and 4–10 days for Staphylococcus. Dried streptococci in the air are not infectious to intact skin. Scratching may spread the lesions.
Impetigo is usually diagnosed based on its appearance. It generally appears as honey-colored scabs formed from dried serum, and is often found on the arms, legs, or face. If a visual diagnosis is unclear a culture may be done to testing for resistant bacteria.
To prevent spread of impetigo to other people the skin and any open wounds clean should be kept clean. Care should be taken to keep fluids from an infected person away from the skin of a non-infected person. Washing hands, linens, and affected areas will lower the likelihood of contact with infected fluids. Sores should be covered with a bandage. Scratching can spread the sores; keeping nails short will reduce the chances of spreading. Infected people should avoid contact with others and eliminate sharing of clothing or linens.
For generations, the disease was treated with an application of the antiseptic gentian violet. Today, topical or oral antibiotics are usually prescribed. Mild cases may be treated with bactericidal ointment, such as mupirocin.
More severe cases require oral antibiotics, such as dicloxacillin, flucloxacillin, or erythromycin. Alternatively, amoxicillin combined with clavulanate potassium, cephalosporins (first-generation) and many others may also be used as an antibiotic treatment. Alternatives for people who are seriously allergic to penicillin or infections with MRSA include doxycycline, clindamycin, and SMX-TMP. When streptococci alone are the cause, penicillin is the drug of choice.
Globally, impetigo affected about 140 million people (2% of the population) in 2010.
Society and culture
It is also known as school sores.
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