Impetigo

• Red sores that quickly rupture, ooze for a few days and then form a yellowish-brown crust
• Itching
• Painless, fluid-filled blisters
• In the more serious form, painful fluid- or pus-filled sores that turn into deep ulcers

Types of impetigo

• Impetigo contagiosa. The most common form of impetigo is impetigo contagiosa, which usually starts as a red sore on your child's face, most often around the nose and mouth. The sore ruptures quickly, oozing either fluid or pus that forms a honey-colored crust. Eventually the crust disappears, leaving a red mark that heals without scarring. The sores may be itchy, but they aren't painful. Your child isn't likely to have a fever with this type of impetigo but may have swollen lymph nodes in the affected area. And because it's highly contagious, just touching or scratching the sores can spread the infection to other parts of the body.
• Bullous impetigo. This type primarily affects infants and children younger than 2 years. It causes painless, fluid-filled blisters — usually on the trunk, arms and legs. The skin around the blister is usually red and itchy but not sore. The blisters, which break and scab over with a yellow-colored crust, may be large or small, and may last longer than sores from other types of impetigo.
• Ecthyma. This more serious form of impetigo penetrates deeper into the skin's second layer (dermis). Signs and symptoms include painful fluid- or pus-filled sores that turn into deep ulcers, usually on the legs and feet. The sores break open and scab over with a hard, thick, gray-yellow crust. Scars can remain after the sores heal. Ecthyma can also cause swollen lymph glands in the affected area.

Causes

Two types of bacteria cause impetigo — Staphylococcus aureus (staph), which is most common, and Streptococcus pyogenes (strep). Both types of bacteria can live harmlessly on your skin until they enter through a cut or other wound and cause an infection.

In adults, impetigo is usually the result of injury to the skin — often by another dermatological condition such as dermatitis. Children are commonly infected through a cut, scrape or insect bite, but they can also develop impetigo without having any notable damage to the skin.

You're exposed to the bacteria that cause impetigo when you come into contact with the sores of someone who's infected or with items they've touched, such as clothing, bed linen, towels and even toys. Once you're infected, you can easily spread the infection to others.

Staph bacteria produce a toxin that causes impetigo to spread to nearby skin. The toxin attacks a protein that helps bind skin cells together. Once this protein is damaged, bacteria can spread quickly.

Risk factors

Although anyone can develop impetigo, children ages 2 to 6 years and infants are most often infected. Children are especially susceptible to infections because their immune systems are still developing. And because staph and strep bacteria flourish wherever groups of people are in close contact, impetigo spreads easily in schools and child care settings.

Other factors that increase the risk of impetigo include:

• Direct contact with an adult or child who has impetigo or with contaminated towels, bedding or clothing
• Crowded conditions
• Warm, humid weather — impetigo infections are more common in summer
• Participation in sports that involve skin-to-skin contact, such as football or wrestling
• Pre-existing chronic dermatitis, especially atopic dermatitis

Older adults and people with diabetes or a compromised immune system are especially likely to develop ecthyma, the most serious form of impetigo.

Complications

Impetigo typically isn't dangerous, but sometimes it may lead to rare but serious complications, including:

• Poststreptococcal glomerulonephritis (PSGN). This kidney inflammation may develop after a streptococcal infection such as strep throat or impetigo. It occurs when antibodies formed as a result of the infection damage the small structures (glomeruli) that filter waste in your kidneys. Although most people recover without any lasting damage, PSGN may lead to chronic kidney failure. Signs and symptoms of PSGN commonly appear about two weeks after an infection. They include facial swelling — especially around the eyes — decreased urination, blood in the urine, high blood pressure, and stiff or painful joints. Most often, PSGN affects children between the ages of 6 and 10 years. Adults who develop PSGN tend to have more serious symptoms than children do and are less likely to make a full recovery. Although antibiotics can cure strep infections, they don't prevent PSGN.
• Cellulitis. This potentially serious infection affects the tissues underlying your skin and eventually may spread to your lymph nodes and into the bloodstream. Left untreated, cellulitis can quickly become life-threatening.
• Methicillin-resistant Staphylococcus aureus (MRSA) infection. MRSA is a strain of staph bacteria that resists most antibiotics. It can cause serious skin infections that are extremely difficult to treat. The skin infection may start as a red, swollen pimple or boil that drains pus. MRSA may also cause pneumonia and blood infections.

Other complications include:

• Scarring
• Lightening (hypopigmentation) or darkening (hyperpigmentation) of the skin

Diagnosis

Doctors usually diagnose impetigo by considering signs and symptoms and medical history and looking at the distinctive sores. Your doctor will likely ask about any recent cuts, scrapes or insect bites to the affected area.

A culture may be necessary to confirm the diagnosis or to rule out another cause. During this test, your doctor uses a sterile swab to gently remove a small bit of pus or drainage from one of the sores. The sample is then cultured in a laboratory for the presence of bacteria.

References:

http://www.medicalnewstoday.com/articles/162945.php

http://www.healthline.com/health/impetigo

https://www.hse.ie/eng/health/az/I/Impetigo/

https://en.wikipedia.org/wiki/Impetigo

http://www.medicinenet.com/impetigo/article.htm

http://kidshealth.org/en/parents/impetigo.html