A Little “Skintelligence” Can Make A Big Difference in Care
BY: Judith Rasband • Aug 23, 2019
An ad for a particular cosmetic product claims the product will penetrate “through nine layers of skin” to better feed and nourish the skin. “Is this really possible?” a reader wants to know.
Dr. Jeremy L. Shuck, M.D., an associate professor and researcher in clinical dermatology at New York University Medical Center, has addressed this question in a very matter-of-fact manner: “No.”
“Maybe a few molecules of anything you apply to your skin will be absorbed into the bloodstream and carried away,” he explains. “But skin cells get oxygen and nourishment from the bloodstream, the way other cells do, not from the outside.”
Other ads claim particular products will speed up skin cell growth and “cellular rejuvenation” for a smoother and more youthful appearance. “Is this possible or even desirable?” asks another reader.
Products are available that contain ingredients that will speed up cell reproduction, such as salicylic acid used in acne medications. However, the use of these ingredients is not recommended for healthy skin. As to the promise of a more youthful appearance, the answer is again, “No.” Such claims boarder on false advertising, say dermatologists.
Let’s face it. If you hope to select effective cosmetic products and to understand skin care principles and procedures, you must first understand the structure of the skin. SO let’s get down to some simple physiology.
Your skin is made up of three distinct layers or stratum: the epidermis, the dermis, and a layer of subcutaneous fatty tissue below. The visible outer layer of skin you see when you look in the mirror is part of the epidermis.
It is the epidermis that we see surface indentations, collectively called pores, which mark the location of hair follicles, sweat ducts and sebaceous oil glands.
Actually, there are several interwoven cell layers even within the epidermis. The topmost layers are actually dead protein cells that form a protective barrier to seal in body fluids and keep potentially harmful objects, chemicals and bacteria.
They prevent most substances from penetrating or being absorbed into the skin below, as Dr. Shuck pointed out. Very few cosmetic ingredients are actually absorbed through the skin and taken into general circulation. Often, those that do penetrate are the culprits responsible for allergic reactions.
In the base of epidermis, new cells are being produced continually. Complete replacement occurs approximately every 20 to 30 days, depending on the area of the body considered. As new skin cells are gradually pushed upward toward the surface by the formation of even new cells underneath, they get farther and farther away from the blood and nutrients they need to survive.
By the time mature cells reach the surface of healthy skin, they are said to be “keratinized” – densely compacted, flat, hard, dry and dead cells. They are flaked or rubbed off, to be replaced by the next layer of cells.
Even the surface cells inside a hair follicle, an oil gland or sweat duct are sloughed off, to be carried up and out with oil secretions. The process of disease may speed or slow the rate of cell reproduction.
With complete replacement of cells and assuming proper skin care, you can look forward to a renewed skin in about three weeks time. This is a natural process and one not needing costly chemical-stripping agents to speed it up in healthy skin.