According to Dr Leslie Baumann, The top layer of the skin, called the epidermis, is made of four distinct layers. When you look at someone’s skin, you see the very top layer, made up of cells that reflect light. When the top layer is smooth, it reflects light evenly so that the skin looks more unformal and radiant than it does when the surface is rougher.
At the lowest portion of the epidermis are mother cells, called nasal cells which produce all the other skin cells. They divide into daughter cells which rise up to the higher levels of the epidermis. As they travel, they age and eventually die, so that they top layer consists of dead cells which naturally exfoliate off in a process called the cell cycle which can take anywhere from 26 to 42 days. Between the thirst and the eight decades of life, the cell cycle claws from 30 to 50 percent of its pace in youth. That means that older skin renews itself much more slowly, forming a rough surface of cells, rather than a smooth surface.
The uppermost cells contain a natural moisturizing factor NMF which holds moisture. The body responds to a dry environment by producing more NMF, but it takes several days for production to rev up, so your skin may become quite dehydrated before help comes. That’s why it is important to moisturize your skin in any dry environment.
Substances released by the cells in the middle of the epidermis form a protective film made of lipids fats that surrounds skin cells and helps keep the skin hydrated your fingers and toes contain fewer lipids and are therefore not as watertight as your legs which is why your fingers and toes look shriveled after immersion in water but your legs do not. Your skin cracks in cold weather because the chilled lipids become stiffer and less able to adjust to movement. The goal of the best moisturizers is to increase the amount of these important lipids, helping your skin to hold moisture.
Source: Dr Leslie Baumann, The Skin Types Solution
Dr. Baumann authored the first textbook about cosmetic dermatology in 2002, and the second edition of Cosmetic Dermatology: Principles and Practice (McGraw Hill) now ranks as the bestselling dermatology textbook in the world and has been translated into 14 languages. In 2005, Dr. Baumann authored The Skin Type Solution, a New York Times bestseller that has been published in many languages. The latest edition of The Skin Type Solutions was published in December 2010 to coincide with the PBS special, “Skin Type Solutions with Dr. Leslie Baumann,” which began airing in late 2010. Dr. Baumann’s latest textbook, Cosmeceuticals and Cosmetic Ingredients (McGraw Hill) was released in November 2014. Dr. Baumann also pens a bi-monthly column in The Miami Herald and regularly contributes to magazines, trade publications and medical journals.The top layer of the skin, called the epidermis, is made of four distinct layers. When you look at someone’s skin, you see the very top layer, made up of cells that reflect light. When the top layer is smooth, it reflects light evenly so that the skin looks more unformal and radiant than it does when the surface is rougher.