What is the main cause of pimples?

What is the main cause of pimples?
Most people develop acne – the most common skin situation – to some degree, but it primarily affects teenagers undergoing hormonal changes.
Acne may be mild (few, occasional pimples), moderate (inflammatory papules), or severe (nodules and cysts). Treatment depends on the severity of the condition.
Acne is primarily a hormonal condition driven by male or ‘androgenic’ hormones, which typically become active during the teenage years. Sensitivity to such hormones, combined with bacteria on the skin, and fatty acids within oil glands, reason acne. Common sites for acne are the face, chest, shoulders, and back, the sites of oil glands.
Acne lesions include whiteheads, blackheads, small bumps, and nodules and cysts.
Fluctuating hormone levels around the time of menses (women)
Manipulating (picking/prodding) acne lesions
Clothing (for example, hats and sports helmets) and headgear
Only three types of drugs have proven to be effective for the treatment of acne, antibiotics, benzoyl peroxide, and retinoids. Most people necessitate at least one or two agents, depending on the severity of their acne.
Benzoyl peroxide, available as an over-the-counter product (for example, Clearasil, Stridex) and by prescription (for example, Benoxyl, PanOxyl, Persagel), targets surface bacteria, which often aggravate acne. Irritation (dryness) is a general side effect.
Retinoids (vitamin A derivatives), for example, Differin, Retin-A, Tazorac, treat blackheads and whiteheads, the first lesions of acne. The most common side effect is irritation. While most are prescription only, there is an over-the-counter version of Differin now available.
Antibiotics, either topically applied to the skin (clindamycin, erythromycin), or taken orally (tetracycline and its derivatives, trimethoprim-sulfamethoxazole) control surface bacteria and reduce inflammation in the skin.
To prevent acne and decrease its damage to your skin, follow these tips.
Choose a cleanser specially formulated for acne. These products often contain salicylic acid or benzoyl peroxide, which helps to clear acne sores.
Clean your face gently, as trauma to the acne breakouts may worsen the acne or reason scarring. When washing your face, use your hands or cotton pads, as any terrycloth or other scrubbing material may cause acne sores to rupture.