Cosmetic knowledge: the pH value of the skin
What is pH?
pH stands for "potentia hydrogenii" and means "the power of hydrogen" - within an aqueous solution. In fact, this value is only measurable and significant in water-containing products. In cosmetics, these would be, for example, products such as emulsions, toners, shampoos, sprays, etc., as opposed to oils, balms, bars, lipsticks, etc. The pH value indicates the concentration of hydrogen ions in a solution. If the hydrogen ion concentration is high, we refer to it as acidic; in the opposite case, as basic or alkaline.
The pH measurement scale ranges from 0 - 14.
- 7 is the middle and is considered pH-neutral – the benchmark here is distilled water
- Acids lower the pH value
- Bases (alkalis) raise the pH value
Our skin surface is slightly acidic – approx. 5 – 5.5. This is sometimes referred to as "pH skin-neutral" and should not be confused with "pH-neutral" (7)! This means: water is already slightly alkaline in relation to the skin.
The skin’s own slightly acidic pH is important. This is how certain metabolic processes can best take place, certain enzymes can develop their effect, and skin-friendly bacteria feel comfortable, while harmful germs have a hard time.
In short: If the pH value is in balance, the defensive strength and the health of the skin increase.
The influence of pH on skin condition
Certain cosmetic ingredients can influence the pH of cosmetic products. For example, soaps and surfactants tend to have a high pH value, while acids, as well as certain plant substances (extracts, etc.), lie in the acidic range.
If we cleanse our skin with strongly basic products, the skin surface is degreased and the skin's own pH is thus thrown out of balance. In addition, the skin swells, water and washing-active substances can penetrate more easily, and the skin barrier is disrupted.
However, the skin has ways and means of restoring its own pH – the "hydro-lipid film" (acid mantle). Through the secretion of sweat (containing, among other things, lactic acid) and sebum, the skin surface is replenished with oil and the pH value is lowered again.
If we use cosmetic products, they can therefore also influence the pH of the skin. As a rule, therefore, care is taken with cleansing and care products to set their pH to be slightly acidic, so that the skin has an easier time bringing its own pH back into balance, or the skin is not as irritated. With certain cosmetic products such as toners (facial toners), a slightly acidic pH is even deliberately chosen in order to bring the skin back to its natural pH after cleansing in a targeted manner and thus support its regeneration.
You can find out how you can specifically adjust the pH of your own homemade products and why this is so important here.