What are wound and skin infections?
Wound and skin infections are the growth and spread of microbes, usually bacteria, within the skin or a break or wound in the skin. These infections trigger the body's immune system and cause inflammation and tissue damage within the skin or wound and slow the healing process. Photo source: CDC, Bruno Coignard and Jeff Hageman
Many infections remain confined to a small area, such as an infected scratch or hair follicle, and usually resolve on their own. Others may persist and, if untreated, become more severe and spread further and/or deeper into the body. Some infections spread to other organs and/or into the blood (septicemia) and cause a body-wide (systemic) infection.
Skin is the body's largest organ and its first line of defense. Even when it is clean, the surface of the skin is not sterile but is covered with a mixture of microbes called normal flora. Most of the time, these microbes do not cause illness and do not stimulate the immune system. If there is a break in the skin or if the immune system is weakened, then the microbes may cause a wound or skin infection.
Wounds are breaks in the integrity of the skin and tissues. They may be superficial cuts, scrapes or scratches but also include deeper cuts, punctures, burns, or may be the result of surgical or dental procedures.
The skin has three layers: the outer epidermis, the dermis – where many hair follicles and sweat glands are located – and the fatty subcutaneous layer. Below these layers are membranes that protect connective tissues, muscle, and bone. Wounds can penetrate any of these layers, and skin infections can spread into them. Wound healing is a complex process that involves many related systems, chemicals, and cells working together to clean the wound, seal its edges, and to produce new tissues and blood vessels.
Skin and wound infections interfere with the healing process and can create additional tissue damage. They can affect anyone, but people with underlying conditions are at risk of slower wound healing and greater risk of wound infections. Examples of conditions that increase the risk of wound infections include:
- Poor blood circulation
- Weakened/suppressed immune system (e.g., HIV/AIDS, organ transplant recipient)
- Low mobility or immobility (e.g., confined to bed, paralysis)
When infections penetrate deep into the body into tissues such as bone, or when they occur in tissue that has inadequate circulation, they can become difficult to treat and may become chronic infections.