Man and PH

It all started with the fact that I was mistaken: it's a shame, it's annoying, but the new soap will have to be redone. I needed to quickly measure the pH of the soap that was put to ripen. When necessary, the pH-meter, as for evil, was not under the hands. I rushed to search the online stores and found it. Oh, how many things I found: from a very smart device for home purposes with LCD indicator displays in the amount of two pieces and calibration at two points for 16,000 Russian money to a pH detector in aquariums for no money. Only it is not clear if "5 ml of aquarium water and 2 drops of indicator are stirred in circular movements and put in the center of the circle … ", then what to do with soap? Soap, as it is not baked, is not aquarium water…
I know the home way to determine the pH from the school hobby of applied household chemicals: ordinary brewed black tea, you throw lemon into it – it lightens, if you add soda – it darkens.
Curiosity and the Internet can work wonders: our attention is provided with the miracle of knowledge of the world, and the centuries-old experience of our inquisitive ancestors, and even beautiful terms that decorate the conversation about chemistry, individual cosmetics, and also allow you to feel yourself in this caste of creators of natural beauty from the outside world.

A hot summer will pass, the stuffiness of noisy streets will be replaced by a golden autumn. Wandering through the alleys and rustling fallen leaves, we will raise our heads to the crowns and admire the bright autumn colors. In the leaves, the production of chlorophyll will decrease, the production of anthocyanins – pigments and flavonoids – begins, to which we owe the charm of autumn.  Angocyanins are pigment substances, usually of plant origin, changing color depending on the pH of the medium. In the food industry, they are indexed as E163, refer to bioflavonoids.  

Rich in anthocyanins, according to Wikipedia, blueberries, cranberries, raspberries, blackberries, black currants, cherries, eggplants, black rice, Concord grapes and nutmeg grapes, red cabbage. To the list you can add: red beet juice, black currant juice, blueberries and strawberries, carrot and cherry juice, turmeric or curry powder, delphinium petals and pink geranium petals, horse chestnut leaves, petals of hydrangea, poppy, daisies, petunias and red peony, petals of red roses, tulips and oregano, onion husks and skins of red radish and eggplant, rhubarb juice.

It is clear that some kind of scale is needed, how the colors of these natural "litmus tests" change depending on the environment. It can be built if you know the acidity of the substances around us: pH
Vinegar 2.0
Orange juice 3.0
Tomato juice 4.0
Milk 6.8
Tap water 7.0 – neutral pH
Baking soda 8.2
Chlorine bleach 11

You can also make strips to measure the pH, for example, from the juice of red cabbage, soaking strips of paper with fresh juice and letting them dry. Knowing the acidity of various substances, the strips can be calibrated.

Indomitable curiosity, I found out even more interesting things. As you know, a person is more than half water. The pH level of water is 7, which is not the most acid-neutral environment. It would seem that why do we need to change the acidity in different organs and tissues? However, in addition to the terribly acidic environment of the stomach, which it needs for digestion, our entire body is not born:

Favorite analysis of biochemists from clinics: pH contents, as is known in the morning on an empty stomach, etc. according to the instructions: 6.0 – 6.4 in the morning and 6.4 – 7.0 in the evenings suggests that the body is functioning normally. A slightly acidic environment is normal, it's even good. Deviations in the direction of urine acidity below 5.0 it is time to talk with doctors about health, and above 7.5 – again to doctors, only we will talk about a sharply alkaline reaction. You can change the acidity by selecting a diet and monitoring changes in acidity.

Saliva also has its own acidity, the acidity of mixed human saliva is 6.8-7.4 pH, but at a high rate of salivation reaches 7.8 pH. If we let things run their course, the acidic environment in the mouth will take advantage of our healthy pofigism, and we will have to go to the dentist, drill innocent teeth, whiten plaques … It is strange that both too alkaline 6.2-6.0 environment and too acidic lead to caries. In general, saliva in the mouth is useful, and its absence is either a sign of excessive excitement or illness.

The normal acidity of a woman's vagina ranges from 3.8 to 4.4 pH, various diseases change it and can apparently help make a diagnosis.

Normal sperm acidity levels range from 7.2 to 8.0 pH. In itself, a deviation from these figures is uninformative, diagnosis can help only along with other information.

Tears are not salty, if you believe the numbers: The acidity of tears is normal – from 7.3 to 7.5 pH, they are almost neutral environment, very, very weak alkali.

I don't know about you, I'm not going to measure the pH in the stomach), but the numbers are for example, from here:
Fecal acidity is normally from 6.0 to 8.0 pH.
The acidity of meconium (the original feces of newborns) is about 6 pH.
Acidity of breast milk – 6,9-7,5 pH

It turns out that the most acid-dependent in the human body is blood. Deviation from the norm is not compatible with life! Our body strives to maintain a stable and normal pH of the blood, goes on to use minerals, salts and substances from other systems and organs.
The acidity of human arterial blood plasma ranges from 7.37 to 7.43 pH, averaging 7.4 pH.
Deviation from the norm in the direction of acidity – below 7.37 is called acidosis, in alkaline – above 7.43 – alcolosis. If the acidity of the blood goes beyond 7.8 pH or below 6.8 pH, we simply cannot live.

Our skin, which we take so care of creating individual cosmetics, is slightly acidic. Scientists indicate different skin acidity from 4.0 to 6.5. The figures depend on the authors using different methods, in particular, the sweat secreted by the body is more acidic than the actual large surface of the skin away from the sweat glands.
Details about skin studies can be found here.
The article gives details of the experiment that allows to compare the effect with the weak acidity and weak alkalinity of the composition used in daily washing. The pH of the skin when using a long-term slightly acidic agent is reduced by about 0.3, when using an alkaline one, there is a short-term effect of increasing the pH of the skin in the direction of alkalinity. The author claims that the classic soap changes the normal bioflora of the skin and destroys the protective acid film created by skin cells and bacteria. Colonies of S. epidermidis bacteria, which are considered a source of unpleasant odor, can be significantly reduced when using products with a pH of – 5. With weak acidity, a decrease in acne was noted, and alkaline agents, according to the authors, disrupt the natural bacterial background and the balance of metabolic processes, which in turn leads to loss of moisture, its roughness and dryness by the skin. That's where citric acid comes from in soap formulas!

In cosmetology, focusing on the "acid mantle", it is considered that the neutral pH is 5.5. There is another point of view, for example, Olga Malysheva, 5.5 is an indicator of the acidity of the upper dying skin scales, just those that are cleaned with a scrub, giving way to new cells. Deep layers are distinguished by a pH close to normal 7.0.
The acidity of the skin varies depending on the place, pH measurements of the upper layer of the skin show 4.5-5.5 on the head, pH of 5.1-5.5 on the chest and pH of 6.2-6.5 on the palms.
Men's skin is more elastic and supple. It has more sebaceous and sweat glands. The pH of men's skin is more acidic.
With acne, the acidity of the skin changes towards alkali, the pH value increases, with psoriasis in the direction of acid. Positive dynamics of pH can serve as a criterion for the correctly chosen treatment.
With age, the composition of the skin becomes more alkaline, dry skin is also more alkaline than oily.

Fellow scientists, associate professors with candidates! Tell me when and what pH in soap to do, I really want to wash once without harm to health!

Proponents of the fact that the skin is slightly acidic and their opponents agree on one thing – the skin and the body protect the stability of the pH, in this case, and we will agree that the neutral pH for your skin should not be very different from your own, if your skin is healthy.

Although manufacturers of soaps and skin cleansers, cosmetic products do not always indicate the pH of the finished product, you can focus on the following figures:

Solid toilet soap has a pH of 9-11. It is believed that it can lead to the formation of calcium and magnesium salts, which in turn leads to peeling of the skin. It seems to me that at such a high pH, it is somehow strange to talk about salts if the balance of the upper layer of the skin from dying cells and deeper layers is disturbed. Apparently, indeed, it is better to wash dishes with gloves with such soap, and for washing hands use soap with a pH not exceeding 7. If the hands dry, use oils, creams or other cosmetics selected individually. It makes sense to handle the skin of the face even more carefully, why spoil the natural metabolic processes in your own skin?

In creams-depilators of alkaline pH, they deal with the hair so actively that they often cause redness and irritation of the skin. Manufacturers often put in the packaging softening slightly acidic agents to neutralize the action of the depilatory.

The pH of the hair in general is very relative – the hair is not a liquid, and the pH measurement is carried out in a liquid medium. Shampoo manufacturers focus on "ecvidermal pH". This charming phrase should be understood in such a way that it corresponds to the pH of hair or skin (they also write about cosmetics for the skin), if only to measure and find out what it is – the pH of the hair, and scientists will not need to argue about the errors of one or another method of measurement.
If you understand the phrase literally, then keratin of human hair is usually digitized as a pH of 5.5, unlike, for example, horses – they have 7.3.

Our favorite procedures in the hairdresser, transforming the appearance and giving us a sense of novelty, also have their pH, deviating towards alkalinity, approximately:

Chemical perm: 6,8-9,1
Toning dyes: 8
Dyes containing ammonia: 9-10
Brightening dyes: 10,5-11
Discolorants: 12-14

To neutralize alkaline components, air conditioners are used. At home, you can use a solution of vinegar, lemon juice (2.5), apple cider vinegar (2.9), beer (4.5).

Fellow scientists, associate professors with candidates! We will have to follow in your footsteps, measure the pH of beauty and health in order to make high-quality individual cosmetics.