To better understand acne, it helps to understand the anatomy of the skin.
The skin contains three main layers:
- The superficial layer that makes up the surface of the skin
- It is composed of skin cells and can be divided into 5 layers based on cell type.
- The top layer of the epidermis, the stratum corneum, is made of dead, flat skin cells that shed about every 2 weeks.
- The thickness of the epidermis varies, according to location: it is very thick over the soles of the feet, and very thin over the ears.
- Lies beneath the epidermis
- Also varies in thickness depending on the location of the skin. It is .3 mm on the eyelid and 3.0 mm on the back.
- The dermis is composed of 2 layers that contain a connective tissue called collagen
- The dermis contains blood vessels, nerves, sweat glands, and hair follicles.
- The number of structures in the dermis varies, according to location.
- The dermis under the arms contains more sweat glands and hair follicles than the dermis on the back.
- Subcutaneous layer:
- Mainly fat and connective tissue.
- Contains blood vessels and nerves.
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- Magin P, Pond D, Smith W, Watson A. A systematic review of the evidence for 'myths and misconceptions' in acne management: diet, face-washing and sunlight. Fam Pract. 2005 Feb;22(1):62-70. 
- Marks R. Acne and its management beyond the age of 35 years. Am J Clin Dermatol. 2004;5(6):459-62.