Types of individual acne lesions
Non-inflammatory lesions
Non-inflammatory lesions: clogged skin follicles known as comedones.
They form due to the combination of dead cells of the skin together with sebum, blocking the follicle. There are two types:
Closed comedones: known as whiteheads. Since these lesions are not exposed to the air and oxygen, they keep their white colour.
Open comedones: known as blackheads. The colour is due to the exposure of the content to the air, producing oxidation and changing it into the black colour. It is not due to a dirty skin or a lack of hygiene.
Inflammatory lesions
Non-inflammatory acne lesions can develop into inflammatory ones when the bacteria present in the skin, Propionibacterium acnes, colonises the hair follicle. That triggers the response of the immune system in the body, meaning that white blood cells are sent there in order to fight the infection. That leads to inflammation and redness of the area. We can differentiate four different types of inflammatory lesions:
Papules: lesions become red and swollen due to inflammation.
Pustules: when the lesions fill with purulent material, containing the whitish or yellowish-looking pus.
Nodules: lesions progress, becoming larger, going deeper into the dermis. They are inflamed and large bumps. They can be very painful.
Cysts: deep and large lesions, filled with pus. When they occur together with nodules, it is called nodulocystic acne.
Acne can also leave secondary lesions like scars and pigmented marks in the area of the lesions
Case of moderate acne with papules and pustules present. Open and closed comedones also present.
