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In fact, the editor found a long time ago that every shampoo will be accompanied by hair loss, but at that time is still young, there is no so-called baldness trouble, also do not care.

However, when washing his hair recently, the editor could obviously feel a lot of hair sliding down his cheek and drifting to the ground under the action of gravity. After washing, facing the bathroom floor, the editor was lost in thought.

Boy, is this the rhythm of going bald?!

Wait a minute, as a rational person who has been ploughing physics for a long time, he must be calm when facing problems.

As the saying goes, know yourself and know the enemy, and a hundred battles will not be defeated. Only through in-depth understanding can we make the most correct judgment and formulate the best strategy.

So today, let's get closer to the world of hair that makes our contemporary people feel anxious.

As you may not know about hair, it is well known that the human body is covered with hair follicles. As long as the hair follicles are healthy, hair can grow.

But life always seems to joke, the hair we most want to keep-hair, seems to be the most vulnerable, while the hair we don't care about or even want to take off seems to be very strong.

Our hair is only 60-90 microns in diameter, so it looks like a silk to the naked eye, but the structure of our hair is actually very complicated.

Wikipedia hair under an electron microscope. From the electron microscope photograph of the hair above, we can see that the surface of the hair is not flat, but is formed by the overlap of many small scales, which is what we often call hair scales.

If you cut the section of the hair from the middle, you will find that its internal structure is very hierarchical.

Hair structure profile | Source: the outermost epidermis (or stratum corneum) of wikipedia, which accounts for about 10-13% of the hair volume, is composed of flat cells stacked with 6-12 layers in the form of scales, which mainly plays a protective role in hair.

To the inside is the cortical layer, which accounts for about 77-80% of the hair volume. Its cellular structure contains a large number of rod-shaped keratin bundles, each of which is intertwined by several helical proteins.

The innermost layer is the medulla, which accounts for about 5% of the hair volume, has a tubular structure, is multi-honeycomb tissue, and is composed of transparent polygonal keratinous fibers.

Hair root hair follicle profile | Source: wikipedia hair is rooted in the hair follicles, and there are hair mother cells in the hair follicles that can produce hair roots, so that the hair can continue to grow.

Only that part of the hair in the hair follicle is active, and the rest outside has no biochemical activity (which can be considered "dead").

Sebaceous glands and erect hair muscles are distributed around the hair follicles, and the oil secreted by the sebaceous glands can lubricate and protect the head.

Hair growth cycle | Source: reference [3] the growth of hair is periodic, with a growth period of 2-6 years at the beginning, during which the hair mother cells in the hair follicles continue to promote the production of hair roots and lengthen the length of the hair. at this time, the hair is relatively stable and not easy to fall off.

After the end of the growth period is about 2-3 weeks of retrogression, this is a transitional stage, the hair begins to "aging".

After the retrogression period is a rest period of 2-3 months, in which the hair follicles stop developing, the hair roots begin to loose and fall off easily under the stimulation of the outside world.

After the hair falls out, the hair follicles enter the next cycle and grow new hair.

Under normal circumstances, hair in the growing period should account for 90-95%, the retrogressive period should be less than 1%, and the rest period should be 5-10%. So even healthy hair is supposed to lose about 100 hairs a day.

Different people's hair may have different characteristics, such as straight and curly in appearance, soft and hard in texture, oily and dry in the degree of oil production, and so on.

At this stage, many theories are trying to explain why hair produces so many traits. The generally accepted theory among scientists is that the shape of hair stem affects the curl of individual hair. If the central axis of the hair is closer to the circle, the disulfide bond in the hair bundle will be reduced accordingly. This means that the chemical bonds in the hair bundle are consistent with each other, making it easier to form straight hair.

02, the use of shampoo is particular about the hair itself, let's take a look at the shampoo that often deals with hair.

Perhaps most of you use shampoo almost every day, but pay little attention to the formula of shampoo (in fact, so is the editor).

The purpose of washing our hair is nothing more than removing dust and oil, and we may need to remove dandruff if necessary, and more advanced ones can do maintenance and care.

So shampoo is a combination of chemicals that can achieve the above functions to make the hair as clean as possible and protect the scalp from damage without side effects.

Here's a list of the ingredients of a shampoo. Let's take a look at it:

Composition table of a brand of shampoo | Source: full of organic chemistry dissuasion feeling taken by oneself.

But don't worry, let the editor take you to sort out what these ingredients are doing.

Surfactant just now we mentioned that the most basic function of shampoo is to remove dust and oil, so surfactant has such a function.

Sodium lauryl alcohol polyether sulfate (also known as sodium dodecyl polyoxyethylene sulfate), coconut oil amide propyl betaine, polydimethylsiloxane alcohol, polydimethylsiloxane, guar gum hydroxypropyl trimethyl ammonium chloride and coconut amide MEA in the composition table all belong to surfactants.

Here I would like to mention two kinds of silicon-containing active agents: polydimethylsiloxane alcohol and polydimethylsiloxane.

These two substances are called silicone oil, which can be adsorbed on the surface of the hair to form a protective layer, which can make the hair bright and smooth and easy to comb. But silicone oil should not be overused, or it will clog the hair follicles and backfire.

Polydimethylsiloxane structural formula | Source: wikipedia Why does a bottle of shampoo put so much surfactant? Because the function of a single surfactant is limited, and excessive use will lead to scalp, hair dryness.

If a variety of surfactants are combined, the dose of each surfactant can be reduced, and at the same time, a "combination attack" can be launched, which is more comprehensive in function and less harmful to scalp and hair.

The function of regulators is generally to adjust the pH value and viscosity of the liquid, so that the shampoo itself is weakly alkaline and moderate viscosity.

However, due to the weak alkaline environment will break the disulfide bond of hair keratin, so we usually shampoo with acidic conditioner for care.

As a matter of fact, the "other" of other ingredients here also contain a lot, but they are simply grouped together because there are not many doses added.

Other ingredients include pearlescent agents, moisturizers, flavors, preservatives, etc., which basically brighten the color, make the hair not dry, increase the flavor as much as possible, prolong the shelf life, and so on.

Special ingredients the special ingredients here vary from shampoo to shampoo. if you want to increase the anti-dandruff effect, like the shampoo pictured above, Piroxone ethanolamine salt is added. Shampoos such as shampoos that require advanced care may also add essences such as baking oil.

If it is a shampoo used by special groups (such as babies), it will reduce the irritating ingredients as much as possible and add milder substances that can achieve a similar effect.

03. How to solve the problem raised by the title? Now let's go back to the starting point. Is hair loss during shampoo a harbinger of baldness?

This should be discussed on a case-by-case basis.

Because the hair has a growth cycle, will fall off naturally, and shampoo contains a variety of chemicals, with a certain degree of irritation.

So when resting hair meets irritating shampoo, there is, of course, only one outcome-shedding. Therefore, a small amount of hair loss is normal when washing hair and flushing.

However, if there is a large amount of hair loss, you should be vigilant, as this indicates that the proportion of hair follicles in the resting period is beginning to increase, and is likely to continue to develop into hair follicle atrophy.

In this way, the hair follicles may not be able to move from rest to growth to start a new cycle.

It should be noted that there is no perfect treatment for hair loss, and some so-called shampoos and health products on the market are likely to outperform their functions.

Therefore, the editor thinks that the most important thing is to develop healthy living habits to prevent hair loss.

As for those hair loss caused by genetic, genetic and other force majeure factors, the editor can only say

references

[1] Hair-wikipedia

[2] Price V H. Treatment of hair loss [J]. New England Journal of Medicine, 1999 (13): 964-973.

[3] Shampoo-wikipedia

[4] Hamel A F, Meyer J S, Henchey E, et al. Effects of shampoo and water washing on hair cortisol concentrations [J]. Clinica Chimica Acta, 2011 (3-4): 382,385.

H ö ssel P, Dieing R, N ö renberg R, et al. Conditioning polymers in today's shampoo formulations-efficacy, mechanism and test methods [J]. International journal of cosmetic science, 2000, 22 (1): 1-10.

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This article comes from the official account of Wechat: Institute of Physics, Chinese Academy of Sciences (ID:cas-iop), author: Eric

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