Final answer:
A pustule is a pus-filled skin lesion caused by bacterial infection, such as by Propionibacterium acnes in acne or by other bacteria in impetigo. Different factors can lead to the formation of pustules, including infection of hair follicles, glands, or the dermal layer, often when the skin barrier is compromised.
Step-by-step explanation:
A pustule is a type of skin lesion that is commonly associated with bacterial infections, such as acne or impetigo. The cause of a pustule is infection of the skin that can be related to bacteria invading damaged areas, like hair follicles or glands within the dermis. For instance, Propionibacterium acnes, which is found on the skin, can lead to the formation of pustules by consuming sebum and secreting enzymes that damage the hair follicle, leading to inflammation and accumulation of pus. In the case of impetigo, pustules can form as a result of bacterial infection and can rupture, becoming encrusted sores.
Certain conditions like folliculitis present as red, pus-filled bumps often due to irritation, sweat, skin injuries, or ingrown hairs. Acne results from clogged sebum-filled pores that get infected and inflamed, sometimes causing pustules. Specific environments, such as the moist and richly nutrient dermal layer, can promote microbial growth if the skin barrier is breached. Furthermore, systemic infections can happen when microbes infiltrate the bloodstream through skin damage.