 Moisturisers or moisturizers (see spelling differences) are complex mixtures of chemical agents specially designed to make the external layers of the skin (epidermis) softer and more pliable, by increasing its hydration (water content). Naturally occurring skin lipids and sterols as well as artificial or natural oils, humectants, emollients, lubricants, etc. may be part of the composition of commercial skin moisturizers. They usually are available as commercial products for cosmetic and therapeutic uses, but can also be thrown together at home using common pharmacy ingredients.
Despite overwhelming promotion of moisturizers for skin care, little proof exists that they provide any health benefits at all.
Epidermis (skin)
Epidermis is the outermost layer of the skin. It forms the waterproof, protective wrap over the body's surface and is made up of stratified squamous epithelium with an underlying basal lamina.
Components
The epidermis is avascular (contains no blood vessels) and is nourished by diffusion from the dermis. The main type or the four principal types of cells which make up the epidermis are keratinocytes, melanocytes, Langerhans cells and Merkels cells. It is a keratinized stratified squamous epithelium.
Layers
The epidermis is divided into many layers where cells are formed through mitosis at the innermost layers. They move up the strata changing shape and composition as they differentiate and become filled with keratin. They eventually reach the top layer called stratum corneum and become sloughed off, or desquamated. This process is called keratinization and takes place within weeks. The outermost layer of epidermis consists of 25 to 30 layers of dead cells.
Sublayers
Epidermis is divided into the following 5 sublayers or strata, listed from the superficial to deep:- Stratum corneum.
- Stratum lucidum (not present in thin skin, only thick, hairless skin of palms & soles).
- Stratum granulosum.
- Stratum spinosum.
- Stratum germinativum (also called "stratum basale").
It is the deepest layer of the skin specifically the epidermis. the anatomical structure of it is composed of a single row of cuboidal of columnar keratinocytes.
Mnemonics used for remembering the layers of the skin (using "stratum basale" instead of "stratum germinativum"):- "Corn Lovers Grow Several Bales" (from superficial to deep).
- "Come Lets Get Some Beers" (from superficial to deep).
- "Before Signing, Get Legal Counsel" (from deep to superficial).
- Californians Love Girls in String Bikinis C-L-G-S-B(from superficial to deep).
Cosmetics
Cosmetics are substances used to enhance or protect the appearance or odor of the human body. Cosmetics include skin-care creams, lotions, powders, perfumes, lipsticks, fingernail and toenail polishes, eye and facial makeup, permanent waves, colored contact lenses, hair colors, hair sprays and gels, deodorants, baby products, bath oils, bubble baths, bath salts, butters and many other types of products. Their use is widespread, especially among women in Western countries. A subset of cosmetics is called "make-up," which refers primarily to colored products intended to alter the user's appearance. Many manufacturers distinguish between decorative cosmetics and care cosmetics.
The manufacture of cosmetics is currently dominated by a small number of multinational corporations that originated in the early 20th century, but the distribution and sale of cosmetics is spread among a wide range of different businesses. The U.S. FDA which regulates cosmetics in the United States defines cosmetics as: "intended to be applied to the human body for cleansing, beautifying, promoting attractiveness, or altering the appearance without affecting the body's structure or functions." This broad definition includes, as well, any material intended for use as a component of a cosmetic product. The FDA specifically excludes soap from this category.
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