Erysipelas is an acute bacterial skin infection that primarily affects the upper layers of the skin, specifically the superficial dermis and the lymphatic vessels. It is characterized by a well-defined, raised, bright red area of inflammation that is often warm, tender, and painful. The infection usually occurs on the face or legs but can appear on other parts of the body as well.
The main cause of erysipelas is infection by certain types of bacteria, most commonly *Group A Streptococcus* (Streptococcus pyogenes). These bacteria are part of the normal flora on the skin or in the throat but can invade the skin when there is a break or damage to the skin barrier. Such breaks can be minor and sometimes unnoticed, including cuts, insect bites, surgical wounds, ulcers, or even skin conditions like eczema or athlete’s foot that disrupt the skin’s integrity.
Once the bacteria enter through these breaks, they multiply and spread rapidly through the superficial layers of the skin and the lymphatic vessels, causing inflammation and the characteristic redness and swelling of erysipelas. The infection triggers an immune response, leading to symptoms such as fever, chills, and general malaise alongside the local skin changes.
Several factors increase the risk of developing erysipelas:
– **Skin injuries or conditions** that compromise the skin barrier, such as wounds, ulcers, insect bites, or chronic skin diseases.
– **Lymphedema**, where impaired lymphatic drainage causes swelling and makes the skin more vulnerable to infection.
– **Venous insufficiency**, which leads to poor circulation and skin changes that facilitate bacterial entry.
– **Immunosuppression**, whether due to diseases like diabetes, cancer, or medications that weaken the immune system.
– **Obesity and older age**, which are associated with reduced skin integrity and immune function.
Less commonly, other bacteria such as *Staphylococcus aureus* can cause erysipelas or similar infections, especially if the infection is deeper or involves abscess formation. In rare cases, infections by *Erysipelothrix rhusiopathiae*, a bacterium associated with animal exposure, can cause a similar skin condition called erysipeloid, which resembles erysipelas but has different clinical features and treatment considerations.
The infection usually starts suddenly with a rapid onset of redness, swelling, and pain in the affected area. The edges of the inflamed skin are sharply demarcated from the surrounding healthy skin, which helps distinguish erysipelas from other skin infections like cellulitis, where the borders are more diffuse. The skin may appear shiny and tight, and blisters or bullae can sometimes form. Nearby lymph nodes may become swollen and tender.
If untreated, erysipelas can lead to serious complications such as abscess formation, spread of infection to deeper tissues, sepsis, or recurrent infections that cause chronic skin changes and lymphedema.
The primary cause of erysipelas is therefore the invasion of the skin by *Group A Streptococcus* bacteria through a breach in the skin barrier, facilitated by factors that impair skin integrity or immune defense. Preventing erysipelas involves maintaining good skin hygiene, promptly treating wounds and skin conditions, and managing underlying risk factors like lymphedema or venous insufficiency.
Treatment typically involves antibiotics, with penicillin being the first-line choice due to its effectiveness against the causative streptococci. Early treatment usually leads to rapid improvement and resolution of symptoms.
