Explaining Biology on Instagram: "How Pimples Form (Acne) A pimple forms when the tiny hair pores on your skin get clogged. 1. Oil gland becomes overactive Your skin has oil glands (sebaceous glands) that make sebum. During puberty, stress, hormones, or oily skin, these glands produce too much oil. 2. Dead skin cells block the pore Normally dead skin cells shed smoothly. But when mixed with extra oil, they stick together and block the pore. 3. Bacteria multiply inside Inside the blocked pore, a