Acne 101: The Different Types of Acne

While acne can manifest in various forms, the two primary categories of acne are non-inflammatory and inflammatory. Understanding the differences between these types of acne is crucial for effective treatment and management.

Non-inflammatory and inflammatory acne both occur when a mix of dead skin cells and debris mix with excess sebum in the skin, resulting in a clogged pore. The clogged pore will lead to non-inflammatory acne (as described below). Inflammatory acne is caused by an infiltration of bacteria into the clogged pore, causing inflammation (as described below).

Non-Inflammatory acne

Whiteheads and blackheads are both types of non-inflammatory acne lesions, often referred to as comedones. They occur when the pores become clogged with excess sebum, dead skin cells, and other impurities. The main difference between blackheads and whiteheads is that blackheads form in open pores, while whiteheads form in closed pores. 

Whiteheads occur when a thin layer of skin covers the clogged pore - trapping the sebum and debris beneath the skin’s surface, keeping it from being exposed to oxygen. Since the air doesn’t reach the pore (aka no oxidation), the contents keep their white-yellowish color and form a closed bump on the skin. 

Blackheads, on the other hand, are open comedones characterized by dark or black spots on the skin's surface. When the opening of a clogged pore is uncovered and exposed to air, the mix of sebum and dead skin cells oxidises and turns black – hence the name.

Inflammatory acne

Papules are small, solid, raised bumps on the skin's surface. They are typically pink or red in color and do not contain pus. Papules result from inflamed hair follicles and are often sensitive to touch. They can be numerous and appear in clusters, making the skin texture rough and uneven.

Pustules are similar to papules in appearance but have a visible white or yellow centre. These round, raised lesions can be sensitive. Pustules develop when bacteria, such as Propionibacterium acnes, infect a blocked follicle and cause an immune response. This causes the pore walls to breakdown and the pore to be filled with pus.

Cysts are one of the two most severe forms of inflammatory acne. They are large lesions that extend deeper into the skin. They appear as pus-filled, painful lumps and may cause significant discomfort. They result from a combination of sebum, bacteria, and dead skin cells accumulating deep within the hair follicles.

Nodules are one of the other severe forms of inflammatory acne. They are large, dome-shaped lesions that develop deep within the skin. Nodules form when clogged hair follicles rupture, leading to a severe inflammatory response. They are often felt within the skin before appearing on the skin surface and can be very painful (even when not touching the skin). They differ to cysts as they’re solid/hard to touch and will not have a tip/whitehead.