Skin is a barrier between the body and the external environment. This function can be fulfilled thanks to the stratum corneum and its structure. The cells of the stratum corneum are tightly connected, which is why they are such an effective barrier. These cells are made mostly of proteins, lipids and water. Intercellular spaces contain lipids, such as cholesterol and its esters, ceramides, triglycerides and fatty acids. A significant factor which determines the properties of the stratum corneum is the pH.

The physiological pH value of skin is 4.0. It results from the presence of fatty acids in the stratum corneum and in sweat, as well as carbonic acid that is produced during cutaneous gas exchange. The physiological pH protects us from the development of microorganisms and is essential for the proper functioning of the skin. Our skin is affected by many factors which can change its pH. After a bath in water, the pH rises to 6.0-7.0, but it soon returns to its natural value (research shows that it takes about 20 minutes). The pH of our skin rises when the secretion of lipase is disturbed and when lactic acid is produced, so the balance between saprophytic and saprobiontic microflora is very important.

The smell of our skin depends on its pH. When the pH is high (above 7), microorganisms start to develop on the skin and the decomposition of bacteria causes an unpleasant smell. The acid-base homeostasis of the skin leads to many questions on measurement methods and the multitude of factors which affect the pH of our skin.

The table shows the pH of the stratum corneum and deeper layers of the skin.

Lipid layer4.5-7.0
Stratum corneum of the epidermis4.0-6.0
Stratum granulosum5.0-7.0
Reproduction layer7.5

Estimated skin pH in specific parts of the body:

Face and body4.8-6.0
Outer part of the handWithin the range of the face and body pH
PalmDepends on the composition of sweat, from 4.5 to 7.0
FeetDepends on the composition of sweat, from 4.5 to 7.0
GroinDepends on the composition of sweat, from 6.0 to 7.0
ArmpitsDepends on the composition of sweat, from 6.0 to 7.0
Elderly peopleThe pH rises and reaches 7.0 or above
Newborns up to several weeks of ageChildren6.55.4-5.9
People with skin conditions such as acne, atopic dermatitis, rosacea and psoriasisSkin surface 4.0-5.0
Female intimate area Naturally acidic, i.e. from 3.8 to 4.5A naturally acidic environment is very important because it is impossible for pathogenic bacteria to grow quickly and multiply easily in an acidic environment.
Male intimate areaThe pH of the genital area is crucial and varies from 4.0 to 5.5