Main Causes of Impetigo in Adults: Staph, Strep, Bullous and Non Bullous

There are two major types of impetigo. These are bullous and nonbullous. Both are most common in children but can also occur in adults. While staph infections are the main causes, strep infections can also be responsible.

Impetigo in adults can occur anywhere in the body but mostly on the face, arms and trunk. Since it is highly contagious, the skin infection easily passes from one person to another and may spread to elsewhere in the body. First symptoms begin with vesicles that quickly break and ooze a clear yellowish fluid. Afterwards, honey-colored crusts form.

Healthy adults do not always require medical attention. Symptoms improve within a period of about 10 days. Regardless, treatment is necessary to prevent complications of impetigo and spread. Antibiotics are the best lines of defense against impetigo although a variety of home treatments are also available. This article discusses the main causes of impetigo in adults, types and how it is treated.

What causes impetigo in adults?

What causes impetigo in adults? How do you get impetigo?  In most cases, staphylococcus bacteria are the cause. These bacteria are usually picked from an infected person or surface. Open sores and pus from impetigo blisters are richest in causative bacteria. Sharing personal items such as clothing, bed linen and clothes can also transmit impetigo-causing bacteria.

Not everyone develops signs of impetigo after coming into contact with causative bacteria. Some factors make it more likely that a certain person will or will not contract infection. These are known as risk factors. They include:

Skin injuries:

Bacteria are almost everywhere. Now and then, we pick up harmful bacteria from other people and contaminated surfaces. The main reason we don’t get sick is because the tough outer skin layer provides protection. The immune system on the other hand fights off any pathogens that may have gotten better of skin barrier. When there are injuries or points of weakness such as caused by cuts, wounds, cracks and conditions like eczema, bacteria easily reach superficial skin layers where they multiply and release toxins which cause infection.

Congested places:

Impetigo is highly contagious. Being in congested places increases one’s chances of coming into direct skin to skin contact with an infected person or contaminated surfaces. This is more common in children attending school or day care centers.

Certain sports:

Sports such as football and wrestling which allow skin to skin contact make it easier for bacteria to be picked up from the skin surface of an infected person. Sharing towels after swimming or gym classes can also spread the infection.

Humid and warm weather conditions:

Bacteria do well in warm and wet conditions. In fact, this is the reason as why impetigo rarely begins on intact areas of skin. They have to reach the lower layer where conditions are warm, wet and nutritious. Incidence rate is higher during summer.

Weakened immunity:

Adults who have been diagnosed with diseases like diabetes and HIV often suffer from weakened immune system. This makes infections more common and aggressive in them. Medications such as mupirocin for impetigo are helpful in controlling bacterial growth so that the immune system can take charge.

Nonbullous impetigo signs and symptoms

Nonbullous impetigo is the more common type which is highly contagious. It most often is caused by staphylococcus aureus. Group A streptococcus bacteria may also be responsible. In industrialized countries, impetigo mostly results from staph infection.

In adults, bacteria are usually picked after extensive contact with a contaminated surface or an infected person. Having skin conditions such as eczema or minor traumas increases chances of infection. Sometimes, the traumas that allow infection into the skin are not even noticeable.

It is rare for nonbullous impetigo in adults to begin on intact skin. This is more common in kids and older people with weak immunity.

Signs and symptoms:

The incubation period lasts between 3 and 10 days after contracting infection. Nonbullous impetigo presents with tiny pustules or vesicles which quickly develop into sores, break open and release a clear yellowish fluid. Afterwards, honey-colored crusts form on the affected areas.

Blisters mostly appear on face, mostly around mouth and nose. Arms and legs may also become infected or any other body area.

It is when nonbullous impetigo blisters are burst open that the infection is most contagious. Coming into direct contact with the open sores or oozing fluid can easily transmit infection.

Since impetigo is not a serious disease, it rarely causes symptoms of systematic illness such as fever, nausea and swollen lymph nodes. When these symptoms occur, they are mild. Severe systematic symptoms may be indications that complications of impetigo have occurred. It can also be that another infection is being confused with impetigo. See impetigo vs herpes for details.

Bullous impetigo in adults

Bullous impetigo is the less common type. It is mainly causes by staphylococcus aureus. When these bacteria enter the skin, they release toxins which cause a gap between the epidermis and dermis. These are the two uppermost layers of the skin. Fluid collects in the formed gap to produce a blister much larger than in nonbullous impetigo. The blisters can reach 3 cm in diameter.

In adults, bullous impetigo can occur in intact skin. Having weak immunity or being constantly in contact with causative bacteria increases the risk of catching infection.

Like in the case of nonbullous impetigo, bullous impetigo blisters also burst and crust over to form dark scabs. This marks final stages of impetigo. Larger blisters may cause scarring but can be avoided by learning how to treat impetigo.

Ecthyma impetigo causes, signs and symptoms

Ecthyma is a more serious type of impetigo. Impetigo blisters are localized to the epidermis. They do not get deep enough to reach the dermis. With ecthyma, ulcers develop below crusted blisters. The ulcers penetrate beyond the epidermis into the dermis. Regardless, the same bacteria that cause impetigo are responsible for ecthyma.


Anyone can get ecthyma. In children and older people, risk of infection is much higher since their immune systems are not as strong as in healthy adults.

Warm and humid weather conditions make it more suitable for bacteria to build and sustain colonies. More bacteria mean more toxins which in turn increase intensity of infection. People living in tropical areas are therefore more predisposed to ecthyma. The infection is also more common during summer.

Other risk factors include poor hygiene and skin injuries. Patient who fail to seek medical attention for impetigo may not recover completely or in a short time. This makes it more likely that infection will become more intense and aggressive, to the extent of reaching the dermis.

Signs and symptoms:

At first, a tiny blister appears which may be surrounded by inflamed skin. The blister quickly burst and gets covered by a hard crust. If the crust is to be removed, a deep ulcer will be uncovered. These ulcers sometimes resolve on their own but leave a scar behind.

Ecthyma mostly results from bullous impetigo. It for this reason is most common on buttocks, feet, legs and thighs. Swelling of lymph nodes may occur.

Treatment is usually necessary for ecthyma. If not treated, patients risk complications such as scarring and more serious infection. Primary treatment option is with antibiotics. Depending on severity of infection, impetigo treatment cream or oral medications will be given.  Conditions or diseases that may have caused ecthyma should also be treated to avoid recurrence. Home remedies such as tea tree oil may help in treatment of impetigo on legs.

Impetigo staph infection and strep impetigo

Impetigo staph infection is the more common type. It is caused by staphylococcus aureus. In most cases, these bacteria are only able to launch an invasion once admitted into the skin by skin injuries or discontinuities.

About 25% of all healthy people carry S. aureus on their skins and nose without any signs of illness. When infection occurs, it may be inform of boils, infected acne, pimples or impetigo. Since these infections are mild, patients rarely experience symptoms of systematic illness.

Strep impetigo is caused by Streptococcus pyogenes or Group A streptococcus. Healthy people sometimes carry these bacteria in their throats or skin without signs of illness. During direct contact, the bacteria are picked and may proceed to cause mild infections such as impetigo or strep throat. These bacteria are at times able to cause infection even on intact skin.

Strep impetigo has a shorter incubation period. Patients experience first symptoms one to three days after contracting infection.

The type of bacteria causing infection cannot be identified through symptoms and signs. Fluid or tissue cultures have to be taken. But since both these bacteria types respond to antibiotics, cultures are usually not necessary. This includes cases of impetigo herpetiformis.

What is MRSA impetigo?

There have been growing concerns among experts that bacteria are increasingly becoming resistant to commonly used antibiotics. What this means is that we may be heading back to the pre-antibiotics era, where a small infection could prove fatal overnight.

MRSA is a good example of bacteria types that are growing resistant to antibiotics. In full, MRSA stands for methicillin-resistant staphylococcus aureus. These bacteria are not resistant to all antibiotics however. They only don’t respond to a class of antibiotics in the class of penicillins.

How it spreads:

MRSA passes from one person to another during direct skin to skin contact. It can also be picked from contaminated surfaces. Pets and animals can also transmit infection. See more here can dogs get impetigo?

It is common to find MRSA infections in body areas covered by hair. Once contracted, it results in a small, red, swollen and warm lump on the skin. The lump is filled with pus which carries a lot of MRSA bacteria. Coming into contact with the pus can easily transmit infection.

How is MRSA treated?

MRSA is not the only type of bacteria to exhibit resistance to some antibiotics. When bacteria are resistant, it means that medications that are supposed to work on them stop having an impact. One of the main causes of bacterial resistance is incomplete use of antibiotic prescription medications. When patients fail to finish their medications, bacteria get the tools needed to develop some form of resistance. The mutated bacteria are then passed on to a healthy person where they make more copies of themselves. This process continues until there is a whole population of a different type of much dangerous bacteria. Other causes of bacterial resistance are use of antibiotics without a prescription and for the wrong purpose. It is very important that a doctor be the one to prescribe antibiotics. Once given, all medications should be taken according to provided instructions. If we fail to observe these simple rules, the situation will just continue to get worse.

There are some types of antibiotics that are able to kill MRSA. Your doctor will prescribe them after diagnosis. Without treatment, MRSA can prove fatal. This is especially when dealing with cases such as impetigo eye, face or nose infection.