The anatomy of the skin and how blemishes form
Understanding how the skin is built helps explain how blemishes form, and why certain active ingredients work. A short anatomy lesson for formulators and product developers.
The three layers of the skin
The skin is the largest organ of the human body and consists of three layers. The epidermis is the outermost layer and provides the waterproof barrier that protects us from the environment. Beneath it lies the dermis, a layer of connective tissue that contains the hair follicles, sebaceous glands and sweat glands. The deepest layer, the hypodermis, consists of connective tissue and fat.
The pilo-sebaceous unit
The key structure for understanding blemishes is the pilo-sebaceous unit: a hair follicle plus its attached sebaceous gland. The gland produces sebum, the natural oil that keeps skin and hair supple. Blemishes arise when this unit becomes congested and inflamed.
How blemishes form
Three factors typically work together. First, increased sebum production makes the follicle environment oilier. Second, dead skin cells accumulate and form a plug in the follicle opening. Third, micro-organisms, in particular Cutibacterium acnes (formerly Propionibacterium acnes), multiply in this oxygen-poor, sebum-rich environment, which triggers visible redness and swelling.
Blemish-prone skin is most common in adolescence, but roughly one in ten cases concerns adults, predominantly women. That is why modern product concepts increasingly distinguish between teen skincare and adult skincare for blemish-prone skin.
What this means for ingredient selection
Because congestion, bacteria and visible irritation each play a role, multifunctional actives are especially valuable. Azelaic acid is a good example: it supports normal keratinization (fewer plugs), has selective antimicrobial activity (targeting opportunistic organisms while sparing beneficial flora) and provides antioxidant support, all in one molecule that is gentle enough for daily use.
Curious how this translates into formulations? Read our application page on cosmetic ingredients for skin prone to acne or discover Azepur99®.
