Impetigo: why is it more frequent in summer?

It is a very contagious skin infection that affects children, but that does not spare adults either.

Impetigo is a highly contagious skin infection that typically affects the most superficial layers of the epidermis.

More frequent during summer and autumn, it spreads easily and is responsible for about 10% of skin problems that affect during the pediatric age, with a peak of prevalence in the range between 2 and 5 years.

However, it is not only children who suffer; Considering all age groups, males and females are affected indiscriminately, but in the adult population it is a more frequent pathology among men.

Impetigo can occur in two different clinical forms:

• Tilbury-Fox impetigo (vulgar or streptococcal impetigo)
• Bockart’s impetigo (staphylococcal impetigo, acute or bullous ostio-follicular).

Let’s see what are the main differences.

	Tilbury-Fox impetigo	Bockart impetigo
Age	Mainly affects children from 5 to 7 years	Affects at all ages
Most frequent period	August, September and early spring	Summer
Cause	Streptococcus	Staphylococcus

The causes of impetigo

The microbes underlying the appearance of impetigo are bacteria, in most cases Gram positive germs belonging to the species Staphylococcus aureus; another bacterium that can cause impetigo is Streptococcus pyogenes, a group A beta-hemolytic streptococcus.

Some risk factors predispose to the development of this pathology, namely:

• poor diet associated with malnutrition
• Diabetes
• poor hygiene
• attend overcrowded environments or kindergartens.

Infections can be primary or secondary; In the first case, the intact skin is infected, while in the second case the infection forms at the level of a wound.

For the skin to become infected, any alteration of its barrier function is sufficient, for example as a result of:

• a trauma
• a cut
• abrasions or wounds
• an insect bite
• a burn
• surgery
• lesions caused by atopic dermatitis or chickenpox.

In fact, damage and ulcers allow staphylococcus and streptococcus to come into contact with fibronectin receptors, the molecule they use to trigger infections.

After the appearance of a first lesion it is very easy for the infection to spread to other areas of the skin apparently not damaged.

It is more frequent in summer

Being struggling with impetigo is more frequent during the summer season and autumn; There could be two factors at play: the higher temperature and humidity in these two seasons.

The optimal growth temperature of Staphylococcus aureus, even in the laboratory, is in fact equal to 35 ° C and the frequency of appearance of impetigo seems to be associated with humidity, with reductions of 40% where the climate is very dry.

The fact that impetigo infection occurs more often in heat and humid environments has also been attributed to the higher incidence of insect bites typical of environments with conditions of this type and to greater exposure to the sun that can reduce the barrier effect of the skin.

In addition, a higher frequency of impetigo has been found in children who wear clothes that expose the limbs to a greater probability of skin-to-skin contact and minor traumas (both phenomena that favor infections); Similarly, its more frequent localization at the level of the legs is justified by a greater risk of trauma in these areas rather than on the arms or back.

Finally, even the sand of the beaches frequented in summer, especially if dirty, can help promote the appearance of impetigo in this season of the year.

Bullous and not bullous

In reality there are two different types of impetigo, which can be bullous or non-bullous.

Non-bullous impetigo is the most frequent form: it corresponds to more than 70% of cases and affects both adults and children; However, it is rare for the latter to contract it before the age of 2 years.

In 80% of cases it is caused by Staphylococcus aureus, while another 10% of cases are attributable to a group A beta-hemolytic streptococcus; In the remaining 10% of cases, the disease is the result of a combined infection by both germs.

Often the first symptom is the appearance of pustules or vesicles that can merge with each other and rupture spreading a purulent exudate that will form crusts of a yellow color similar to honey; moreover, often the non-bullous impetigo has at its base an erythema.

Generally more blisters appear, both on the face and on the limbs, especially in areas where the skin is damaged; The vesicles then spread quickly to seemingly undamaged areas of the skin.

Another symptom often associated with non-bullous impetigo is a slight enlargement of the lymph nodes, while more general symptoms, such as fever, are generally absent.

Bullous impetigo is more common in young children, so much so that most cases (as many as 90%) occur under 2 years of age.

It is almost exclusively caused by Staphylococcus aureus, which in this case triggers the formation of small blisters that turn into flaccid bubbles.

In this form of impetigo, staphylococcus produces a substance (exfoliative toxin A) that causes loss of adhesion between the cells of the superficial layers of the skin.

Compared to non-bullous impetigo, bullous impetigo is not associated with the appearance of crusts; the bubbles – filled with a transparent or yellow liquid, which can become dark or purulent – rupture leaving an erythema delimited by scales.

Generally, the lesions (less numerous than those that appear in the non-bullous form) are formed in areas where there is the possibility of rubbing skin against skin, on the trunk and, unlike what happens in non-bullous impetigo, on the membranes of the mouth; The lymph nodes do not enlarge, while generic symptoms such as fever are more frequent than in the non-bullous form.

Finally, impetigo can affect tissues even deeper. In this case it is called ectima and is characterized by ulcers that penetrate into the thickness of the dermis.

Typical ecthyma ulcers have purplish margins, can be purulent and may be associated with honey-yellow or dark brown crusts.

Possible complications

The most common complication of impetigo is the spread of the infection to other areas of the body besides those where it appeared, including hands, neck, and scalp.

To favor this complication is also the stimulus to scratching with the nails due to the itching associated with the blisters.

Other possible complications concern the kidneys; Even rarer are cases in which impetigo irreparably damages the skin or leaves scars.

In general, the lesions heal slowly, but unfortunately in young children they tend to reappear.

Consulting a doctor is always the most suitable choice to deal with the problem; The therapy is in fact based on specific treatments.

Impetigo: how to cure

Impetigo can be treated topically, for example with an antibiotic ointment; However, the use of creams may be necessary to combine oral antibiotic therapy.

The active substances used should be active against both Staphylococcus aureus and Streptococcus pyogenes.

Their action helps to significantly reduce the duration of infection and the spread of lesions; In addition, antibiotic treatment reduces the risk of kidney complications, as well as problems with joints, bones and lungs or rheumatic fever.

In general, the topical route is the one chosen in case of localized and uncomplicated non-bullous impetigo; Before applying the ointment it is necessary to remove the crusts with soap and water.

Oral antibiotics are instead prescribed in case of bullous impetigo and if non-bullous impetigo is associated with the presence of:

• more than 5 lesions
• Symptoms of a systemic infection
• enlarged lymph nodes
• lesions inside the mouth
• deep tissue involvement.

The most used active ingredients topically are mupirocin, retapamulin and fusidic acid; Those most commonly used orally include cephalosporins, the amoxicillin-clavulanate combination, dicloxacillin and cephalexin.

In particular, in the event that diagnostic investigations reveal that the infection is caused by streptococcus alone, the chosen therapy could be based on penicillin (not suitable, however, in case of allergies to this antibiotic).

Finally, in case of resistance to methicillin, trimethoprim-sulfamethoxazole may be effective, but if the infection is associated with a group A streptococcus it is still necessary to use an antibiotic that is effective against this bacterium.

Behavioral norms

To allow healing from impetigo it is also important to pay attention to personal hygiene and to avoid coming into direct contact with other people to whom the infection could be transmitted.

In particular, it is necessary to wash well clothing, linen, towels, hands and other parts of the body that may have come into direct contact with the infected areas.

Lesions should also be cleaned; Just use soap (possibly containing antiseptic active ingredients) and hot water.

Crusts should be removed and lesions should be kept properly covered or bandaged, again to limit the risk of transmission of the infection to other people or its spread to other areas of the skin.