Can minerals be absorbed through the skin? When summer arrives and temperatures rise, many of us are drawn to the sea. Then it is time to swim, drift and enjoy the feeling of salt water on our skin. When it comes to saltiness, not all seas are equal.
While the salt content is rather low at around 1.8% in the Baltic Sea, it is up to 33% in the Dead Sea. This raises the question: How deep does salt get under the skin? Can salt enter through the skin into the blood?
Skin: the human body’s largest organ
The skin is our largest organ. If we could spread it out, it would fill an area of up to two square meters in adults. It will weigh about 14 kilograms – about 20 percent of our body weight.
It consists of three main layers, which in turn are divided into further layers and have several functions:
The subcutis consists of connective and fatty tissue. It stores nutrients, regulates the heat balance and protects the bones from shocks. The dermis ensures that the skin remains firm and elastic.
The dermis also contains blood vessels that supply the skin cells with nutrients and sensory cells that react to heat, cold and touch. The outermost layer visible to us is the epidermis. Skin appendages such as hair follicles, sweat and oil-producing glands are located in the dermis, but pass through the epidermis.
Protective layer of skin
One of the most important tasks of the epidermis is to protect us from foreign substances and microorganisms. The uppermost layer of the epidermis, the horny layer, is essentially a protective wall.
It consists of cells that migrate upwards from the lower layers, die and cornify in the process. These dead cells are forming brick-like layers while fats hold them together.
If foreign substances want to enter the body through the skin, they have to overcome this wall of cells.
As these cells are water-repellent, fat-soluble (lipophilic) substances are able to overcome the this layer and enter deeper into the skin. Mineral salts decompose into ions in water and are not fat-soluble.
Therefore they remain on the epidermis and cannot penetrate into the dermis where the blood vessels are located.
Another way for the ions to penetrate the dermis would be to pass through skin appendages such as hair follicles, sweat and oil-producing glands.
However, their proportion on the surface of the skin is so low at 0.1% to 1% that the amount of salt that could penetrate the skin above them is extremely small.
However, if a substance is fat-soluble, very small (with a molecular mass of less than 500 Dalton) and has a melting point that is not too high (below 200°C), it could overcome the skin barrier.
Medical applications of this mechanism are already available. Transdermal patches such as nicotine patches or pain-relieving plasters bring active ingredients through the skin into the bloodstream.
In this way they do not have to pass through the stomach and intestines, remain chemically unchanged and can exert their effect directly at the appropriate place.