The oil film of the skin is a chemical, slightly acidic fat-water layer on the surface of the skin, composed of the secretions of the sebaceous and sweat glands. This layer acts like a chemical barrier to pathogens. Skin that is too dry can break down this barrier function.
What is the oil film?
The skin‘s oily film is a chemical, slightly acidic fat-water layer on the skin’s surface composed of secretions from the sebaceous and sweat glands. Human skin carries a natural film of water and fat. This film originates from the skin glands, which can be divided into sebaceous and sweat glands. They terminate in exit ducts and contractile gland endings at the skin surface. Sweat, as well as sebum and degradation products of cornification processes are released from these ducts. The secretions of the skin glands form the greasy film on the skin. Since the beginning of the 20th century, the natural water-fat film is sometimes also referred to as the acid mantle of the skin. In previous centuries, physicians had already discovered that the entire skin is covered by such an acid layer. In the 20th century, the physician Alfred Marchionini drew new conclusions about the function of this acid film. The weakly acidic ph value of the skin in humans is between four and seven and, according to Marchionini, is primarily intended to protect the epidermis from pathogens by warding off bacteria. However, since some bacteria can also thrive in a slightly acidic environment, this theory is now subject to criticism. Thus, according to current science, the antibacterial function of the water-fat film is not thought to be due to acidity, but to the peptides and lipids contained in the fat film.
Function and task
Several glandular secretions are contained in the natural oily film of the skin. The secretions of the sebaceous glands and the sweat glands meet in the greasy film and differ tremendously in their ingredients. In addition to uric acid and water, the final greasy film contains mainly electrolytes, urea, peptides and fatty acids. The most important electrolytes in the human body are salts such as sodium, potassium, calcium or magnesium, which dissociate in the electric field. Uric acid is mainly found in human sweat and acts as an antioxidant. Urea, in turn, is a detoxifying substance that contains a certain amount of toxic ammonia. Peptides are bacteria-resistant molecules made of amino acids. Fatty acids, in turn, come from the sebaceous glands. Important acids in this context are above all the omega-3 fatty acids, which are crucial components for the moisture balance of the skin. These components are not only excreted externally, but are also deposited in the horny layer of the skin. Numerous fats are stored especially between the individual horny cells, binding the cells together like mortar. This is what makes the skin water-repellent in the first place and gives it a supple surface. The skin flora is ideally adapted to the chemical biotope consisting of the substances mentioned. This means that the protective germs of our own skin can easily withstand the chemical environment of the fat film. For other microorganisms, however, the biotope consisting of the specific compounds of the mentioned components often acts as a chemical barrier. The secretions from the skin glands thus protect the human skin and mucous membranes from the growth of foreign microorganisms. In addition, the fatty film prevents the skin from drying out or cracking. Consequently, the general resistance and durability of the skin layers depends not least on the water-fat film of the skin.
Diseases and ailments
Dysfunction of the skin glands can alter the composition of the natural oil film on the skin surface and manifest itself in various symptoms. Extremely dry skin, for example, may refer to pathological phenomena related to the lipid mantle. The possible causes of dry skin and thus disturbed fat film production are manifold. In addition to metabolic disorders such as diabetes or malfunctions of the thyroid gland, hormonal disorders can also be considered as a cause. Under certain circumstances, however, the patient also drinks too little or follows harmful hygiene rituals. Skin care with alkaline products, for example, can cause the skin to dry out, as alkaline substances flush the lipids out of the horny layers.Even eating disorders, alcoholism and other addictive diseases can change the composition of the natural oil film on the skin and thus cause the skin to dry out. However, the horny layer in particular still dries out most frequently due to excessive contact with water, cleaning solutions or solvents. Although the lipid film can regenerate to a certain extent, certain hygiene habits or everyday contact with solvents all too often overtax the skin’s ability to regenerate. The barrier function of the skin can thus soften in the worst case. Germs and bacteria now have an easy time colonizing the skin and chemical pollutants are also only kept out to a limited extent. Eczema or other skin diseases often develop as a result. If such complaints are recognized early enough and the life situation is changed for the sake of the natural oil film, the skin can regenerate completely in most cases. If, on the other hand, the harmful habits are continued, dry skin can develop into an even greater health problem. In extreme cases, for example, the horny layer of the skin is attacked. Without the natural oil film, there are hardly any fatty acids between the horny cells and the cells no longer hold together ideally. As a result, the skin becomes cracked and decrepit.