During puberty, hormone levels increase, activating these glands which cause the production of oil, or sebum. For many, this can lead to an increase in dead skin cells, or corneocytes, a process called follicular keratinization. This activity creates a "plug," or microcomedone. From there, it may develop into a blackhead or a whitehead, or in more extreme cases, severe acne.

1. Follicular Keratinization

   Excess skin cells build up on the surface of the skin, clogging the pore.

2. Sebaceous Activity

   An increase in androgen hormones, a type of male hormone, increases oil production. Excess oil, called sebum, mixes with the dead skin cells, causing a blackhead.

3. Inflammation

   An inflammatory response causes redness and swelling.

4. Propionibacterium Acnes (P. Acnes)

   This bacteria lies deep within the pore and can break down the heavy oil in the sebaceous gland, which causes inflammation and results in blemishes and breakouts.