Why do you have sebum glands?

Glands that produce sebum, known as «sebaceous glands», are attached to the sheath of each hair follicle.
The number of glands can vary, but typically, one to four sebaceous glands are associated with each hair.
Hair follicles are found almost everywhere on the human body, except for: the palms of the hands, soles of the feet, lips, eyelids, penis, labia minora and most of the nipples.
The face and scalp have the highest concentrations, with up to 6,000 glands per square inch.

Sebum is an oily, waxy substance that is unique to mammals.
It's a natural lubricant.
Sebum prevents moisture loss by creating a waterproof barrier, preventing excess water from evaporating from the skin, and keeping it hydrated.
It's sebum that gives hair its shine.

There is no passage for sebum to escape from the glands, except between the hair shaft and its sheath.
Sebum is only ejected when the hair is forcibly bent.

Since humans do not touch their skin, the sebaceous glands continue their production; therefore they enlarge.
The skin of the whole body dries out.
Blocked sebaceous glands create pimples and blackheads, and can lead to more serious skin problems

Here's how it works.
It's a mechanical system.
Sebum is expelled when your nails bend the hair shafts while raking the skin.

• As your nails pass over your skin, they bend the base of the hair they encounter.
• This creates a mechanical pressure on the sebaceous glands to release some of the sebum.

HOW SEBUM IS EXPELLED

Humans are primates.
Only primates have flat nails that can scrape the skin without hurting it.
All primate species groom their skin, every day, for extended periods; except humans.
There is no doubt that our ancestors were grooming in the past, and that we stopped doing it at some point in our evolution.

Grooming is a natural behavior in primates that dates back approximately sixty million years.
Modern humans have concluded that grooming is useless; and their exploding sebum glands are just one of the many health problems this decision has caused.

There are about six times more sebaceous glands on your head, where you are more folded, and where more grooming is needed.
Hair varies in size all over your body.
To equalize their lubricating effect, sebum glands are;
• Larger on smaller hair (neck) and
• Smaller on bigger hair (beard).
On a human fetus, these same sebum glands secrete the white substance called Vernix caseosa; another waxy and oily compound that facilitates the fetus's passage during birth.

Sebum production becomes problematic on the scalp.
Unlike the rest of the body, the sebaceous glands located there are activated by the movement of long hair.
The wind, your brush or comb, your pillow, ... all these elements exert pressure on the sebaceous glands, prompting them to release their contents.
But, without regular scalp grooming, the sebum stays there.
It accumulates and mixes with other substances like sweat, dead skin cells, and hair products.
This buildup hardens, and forms a crusty and scaly layer on the scalp.
If left untreated, this sebum buildup can lead to dandruff, acne, local skin infection, and even hair loss.

We all have witnessed sebum eruptions that far exceeded what we would expect from a few glands.
My grooming experience demonstrates that the most problematic sebum build-ups are not found in the glands themselves.
They are the result of having several glands expelling their content inside a skin fold, or a fold crossing, where the sebum accumulates.

The output from several glands is expelled inside cutaneous folds, but mainly at their crossings.
However, since dermatologists don't recognize cutaneous folds (they think they are lines), this phenomenon remains poorly understood.
Bad advice then follows.

Human grooming lets you use your nails to treat all kinds of skin and health-related problems.
The following video will get you started: