Acne is a common skin condition characterized by the presence of inflamed or non-inflamed lesions, such as pimples, blackheads, whiteheads, and cysts, primarily on the face, chest, upper back, and shoulders. It occurs when hair follicles become clogged with dead skin cells, oil (sebum), and bacteria, leading to the development of various types of lesions. The causes of acne are multifactorial. It includes:

1. Excess Sebum Production: Sebaceous glands in the skin produce an oily substance called sebum. In people with acne, these glands may produce excessive amounts of sebum, which can contribute to clogged hair follicles.
2. Hair Follicle Blockage: Dead skin cells shed regularly and should be shed away from hair follicles. In individuals with acne-prone skin, these cells can become sticky and block the opening of the hair follicle, leading to the formation of comedones (blackheads and whiteheads).
3. Bacterial Growth: The skin bacterium Propionibacterium acnes(P. acnes) is commonly found on the skin and is not inherently harmful. However, in clogged hair follicles, it can multiply rapidly, leading to inflammation and the formation of inflamed blemishes.
4. Inflammation: The immune system responds to the presence of bacteria and blocked follicles by releasing inflammatory molecules. This can result in redness, swelling, and pain associated with acne lesions.
5. Hormonal Factors: Hormones play a significant role in acne development. Androgens, a group of hormones including testosterone, can stimulate the sebaceous glands to produce more sebum. Hormonal fluctuations, such as those that occur during puberty, menstruation, pregnancy, and certain medical conditions, can contribute to acne flare-ups.
6. Genetics: Family history and genetics can also play a role in an individual’s susceptibility to developing acne.
7. Diet: While the role of diet in acne is still debated, some studies suggest that high-glycemic-index foods (such as sugary and processed foods) and dairy products might be associated with an increased risk of acne.
8. Stress: Chronic stress can potentially worsen acne by influencing hormonal activity.
9. Environmental Factors: Exposure to pollutants and certain cosmetic products may also contribute to the development or exacerbation of acne.