Impetigo

Contagious impetigo

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

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.

Ecthyma

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.

Causes

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.

Predisposing factors

Impetigo is more likely to infect children ages 2–5, especially those that attend school or daycare. 70% of cases are the nonbullous form and 30% were the bullous form. 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.

Transmission

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.

Diagnosis

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.

Differential diagnosis

Other conditions that can result in symptoms similar to the common form include contact dermatitis, herpes simplex virus, discoid lupus, and scabies.

Other conditions that can result in symptoms similar to the blistering form include other bullous skin diseases, burns, and necrotizing fasciitis.

Prevention

To prevent spread of impetigo to other people the skin and any open wounds 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.

Treatment

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. In 95% of cases, a single antibiotic course results in resolution in children. It has been advocated that topical disinfectants are not nearly as efficient as antibiotics, and therefore should be avoided.

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.

Alternative medicine

There is not enough evidence to recommend alternative medicine such as tea tree oil or honey.

Prognosis

Without treatment people typically get better within three weeks. Complications may include cellulitis or poststreptococcal glomerulonephritis. Rheumatic fever does not appear to be related.

Epidemiology

Globally, impetigo affects more than 162 million children in low to middle income countries. The rates are highest in countries with low available resources and is especially in the region of Oceania. The tropical climate and high population in lower socioeconomic regions contribute to these high rates. In children in the United Kingdom under the age of 4 are 2.8% more likely to contract impetigo and rates decreases to 1.6% for children up to 15-years-old. As age increases, the rates of impetigo declines but all ages are still susceptible.

History

Impetigo was originally described and differentiated by William Tilbury Fox.

Society and culture

It is also known as school sores.