What causes acne?

Acne is primarily caused by a bacterial infection of the sebaceous glands, specifically due to the overgrowth of a type of bacteria known as Propionibacterium acnes (now known as Cutibacterium acnes). These bacteria thrive in the hair follicles and sebaceous glands, particularly when there is an excess production of sebum, the oily substance that lubricates the skin.

When the sebaceous glands become clogged with sebum and dead skin cells, this creates an environment conducive to bacterial growth. The bacteria multiply, leading to inflammation and the formation of acne lesions such as pimples, cysts, and pustules. The inflammatory response can also result in redness and swelling around the affected areas.

Other options like viral or fungal infections are not the primary causes of acne. Similarly, while allergic reactions can cause skin issues, they do not specifically lead to the formation of acne lesions. Thus, the correct answer highlights the role of bacteria in the development of acne, which is a key factor in understanding this common skin condition.