Final answer:
Secondary lesions are changes in the skin that result from the progression of an initial skin lesion. These can be caused by a variety of factors, including hypersensitivity reactions, infections, and the skin's healing process forming scar tissue.
Step-by-step explanation:
Secondary lesions are changes that occur in the skin due to the progression or manipulation of a primary lesion. Factors such as pain sensation and the presence of skin lesions can increase susceptibility to secondary injuries and infections with other pathogens. For instance, when someone experiences contact dermatitis, like when exposed to latex, or delayed-type hypersensitivity reactions such as the tuberculin skin test, these primary conditions can sometimes evolve into secondary lesions. Skin cancer and burns can also result in secondary lesions, particularly when the skin attempts to repair itself and scar tissue forms as a result of fibroblasts generating collagen.
Injuries or damage to the skin can compromise its integrity, making it easier for microbes to invade and cause various types of skin infections. These can range from localized infections, such as folliculitis and acne, to systemic infections if the microbes reach the bloodstream. Likewise, delayed hypersensitivity, a type of cell-mediated immune response that is often associated with contact dermatitis, can lead to the development of secondary lesions upon repeated exposure to certain substances.