Purulent Skin Infections

Purulent skin infections (pyoderma) are a group of bacterial diseases. They are very common, they can affect individuals of any age and sometimes they can cause very serious complications.


The most common causative agents are bacteria belonging among staphylococci and streptococci, which penetrate the skin through various cracks or through hair follicles. The risk of infection is increased by various injuries, burns, chronic venous ulcers and other disruptions of the skin cover. People with weakened immunity are more prone to purulent skin infections.



This infection is caused by staphylococci and it occurs mainly in children. It manifests as an erythematous rash with blisters. The blisters contain a yellowish content and after their rupture there develops a yellowish crust. The infection can affect virtually any part of the skin including the head and the scalp. If staphylococci infect a primary non-infectious skin inflammation, we talk about the secondary impetiginization.


Folliculitis is inflammation of hair follicles. Bacterial folliculitis is usually caused by the staphylococci. Surrounding of the inflamed hair follicle is red, painful and swollen and a festering pustule may occur.

Boil (furuncle)

A boil is a complication of folliculitis. It is much more serious and locally spread infection that (unlike the folliculitis) heals by a scar formation.


A carbuncle is localized infection where more boils merged together. It is a fairly extensive inflammatory process and, without proper treatment, it can form large abscesses or sepsis.


Erysipelas is an infection of both the skin and subcutaneous tissue caused by the streptococci. It typically affects lower limbs that are already plagued by chronic venous insufficiency and venous leg ulcers. The affected body part is red, painful and swollen and the patient usually suffers from high fever. The disease irreparably damages the lymphatic veins and often recurs.


Phlegmon means the spread of infection through the skin and subcutaneous tissue deeper to the muscular layer. It is a more serious process than erysipelas.


The diagnosis is usually easily done by physical examination of the patient and can be confirmed by a dermatologist.


The therapy depends on the severity of current infection. Less serious cases can be treated only by antimicrobial and healing ointments supported by increased hygiene. More serious cases are treated by antibiotics that are administered orally or intravenously. Larger abscesses must be treated surgically (cutting and evacuating the pus). A phlegmon endangering the basic vital functions may be an indication to amputation of the affected body part.


Jiri Stefanek, MD  Author of texts: Jiri Stefanek, MD
 Contact: jiri.stefanek@seznam.cz
 Sources: basic text sources