Skin’s immune system
Skin’s immune system is ready to ward off attacks from the environment. As the outer border of our body with the surrounding our skin fulfils important protection and defensive tasks. Several mechanisms interact in this process.
The mechanical protection is performed by the horny layer.
The microbial protection, i.e., skin flora or skin microbiome, inhibits the growth of dangerous pathogens.
The chemical protection is built by the acid protection mantle.
Skin’s immune systems functions as a guard reacting with defensive measures in case of penetration of harmful organisms.
Skin’s immune system is capable to differentiate between the multitude of germs which are part of the skin flora and strange organisms which threaten skin.
Expecting injuries or infection, the dendritic cells near skin’s surface build the front line. They act as an early warning system. They are the first to detect dangerous organisms and inform other immune cells.
In addition, there are antimicrobial peptides in the skin cells that are able to destroy viruses, bacteria or fungi within seconds.
These antimicrobial peptides (AMP) are produced in the epithelial cells of several organs and in neutrophile granulocytes or leucocytes and are responsible for the repulsion of microorganisms on skin and mucous membranes. Defensins count among them.
They are elements of the congenital or unspecific immune system and are highly concentrated in mother’s milk.
In addition, several different white blood cells continually are patrolling in blood and lymph and are also present in skin’s immune system.
In case of skin injuries, neutrophiles meet at the point of damage. They are the most frequent type of white blood cells and elements of the unspecific immune system. The repel microorganisms, foreign bodies, bacteria, viruses, fungi, parasites. They attack the penetrating germs and destroy them. The waste material resulting from the process is removed by phagocytes or macrophages.
The macrophages carry the foreign organisms to the B-lymphocytes that mark those antigens with antibodies. Subsequently, the T-killer cells become active and destroy the foreign organisms with special chemical substances.
The release of antibodies is activated by T-helper cells in case of repeated encounters with the antigen.
However, if antibodies have not yet been produced, protection mechanisms exist. The antigen activates T-killer cells. They kill the viruses and the infected cells. The T-lymphocytes sensibilized by the foreign organisms build a memory of the encounter; therefore, they are called T-memory cells. In case of a second encounter, the T-helper cells arrange a faster and stronger reaction by triggering the production of antibodies.
Skin’s immune system: congenital and acquired
Two systems work together in protection and defense: the congenital or unspecific immune system and the acquired immune system.
The congenital immune system is active already in newborns. It includes, among others, the dendritic cells near skin’s surface and the neutrophiles.
The acquired immune system becomes active by learning processes after birth. It includes
B-cells and T-cells which are everywhere in the body, also in skin’s immune system.
The B-cells are produced mainly in the intestines and the bone marrow, the T-cells in the thymus.
While the B-lymphocytes presents antibodies, the T-cells are able to differentiate body’s own from foreign substances. When they detect a foreign body, they build messengers to attract other immune cells. T-helper cells are important organizers of the tasks of the immune system.
Plant active agents for the immune system
Certain active substances derived from plants provable are able to support our defenses and skin’s immune system. Science explains the working mechanisms of plant active agents that are used also in cosmetics and discovers more and more details of the immune modulating effects.
Many plant extracts traditionally used in Ayurvedic medicine have antioxidative, antiviral, antibacterial effects.
Some examples:
Curcuma longa
Turmeric or curcuma is a ginger plant. The active components are extracted from the root. The anti-inflammatory properties were known already in Marco Polo’s age.
The yellow-orange substance is a polyphenol. Its is said to have life-prolonging effects because it destroyed senescent cells in experiments on mice. Recent studies explain its immune-promoting effects. Curcumin contains a very effective immune modulator that supports the activity of T-cells, B-cells, macrophages, neutrophiles, killer cells and dendritic cells.
In-vivo and in-vitro tests proved that in curcumin anti-inflammatory and immune modulating effects are combined and strengthen the immune system.
The antiviral effects are said to be active against dengue, influenza A, hepatitis B and herpes simplex virus.
In cosmetics, Curcuma Longa (INCI: Curcuma Longa Root Extract) is used, e.g., in face creams to strengthen skin’s barrier, face masks, glow serums, vitalizing shampoos/rinses, deodorants.
Andrographis paniculata
Kalmegh, with botanical term Andrographis paniculata, also known as king of bitters due to the high concentration of bitter substances, has played an important role in Ayurvedic medicine because of its detoxifying effect. The extract protects the liver and the respiratory system. Recent studies prove its anti-inflammatory effect and its effectiveness for colds and sinusitis.
The active components are andrographolides responsible for the bitter taste.
They are able to modulate the congenital immune system by up-regulating β-defensin-2, activating macrophages and the production of antibodies.
Kalmegh extracts feature virus-killing activity against Herpes Simplex and influenza viruses and are also effective for uncomplicated and influenza infects. They shorten the duration of cough, sore throat and accelerate recovery.
In cosmetics, kalmegh (INCI: Andrographis Paniculta Extract) is used for its astringent, skin-caring and brightening effects, e.g., in day care, anti-spot products.
The repair of oxidation-caused cell damages is based on the extract’s proved diminishing effect on the production of isoprostane-8.
Ocimum sanctum
Indian or holy basil or tulsi has a long tradition in Ayurvedic medicine and has immune-boosting effects which were demonstrated in double blind studies. An alcoholic tulsi extract could raise the levels of IFN-γ and IL-4 and the percentage of T-helper cells and T-killer cells significantly.
Interferon gamma (IFN-γ) is a cytokine mainly produced by T-lymphocytes with immune-stimulating, antiviral and antitumoral properties.
Interleukin IL-4 triggers the differentiation of T-helper cells to T-cells.
In cosmetics, tulsi (INCI: Ocimum Sanctum Leaf Extract) is used, e.g., in face cream with barrier-strengthening effects, eye creams that enhance skin’s radiance, protection and nourishing creams that regulate impure skin, cleansing products, shampoos and hair oil.
Emblica officinalis
The Indian gooseberry or amla features antimicrobial and anti-inflammatory powers. The immune modulating properties are based on bioactive tannins and polyphenols. They are able to inhibit mediators in inflammation processes (like NF-xB signal paths), to regulate
T-killer cells and cytotoxic activities of lymphocytes.
In vitro, the antiviral potential of amla proved to inhibit Coxsackie virus, Herpes Simplex and influenza viruses and the HIV-transcriptase enzyme.
In cosmetics, amla (INCI: Emblica Officinals Fruit Extract) is used, e.g., in anti-aging/ anti-wrinkle products to stimulate collagen synthesis, sun protection products, brightening skincare, products for plant-based hair-coloration, shampoos for normal, repair-needing or sensitive hair, in hair oils, shower creams.
Salacia reticulata
The antioxidant, anti-mycotic, antibacterial and antiviral potential of Kothala Himbutu is based on the high concentration of saponins and triterpenoids. The powder from the root is said to have anti-diabetic and fat-reducing effects.
The antiviral activity could be proved on H1N1-infected mice. The working mechanism uses the activation of T-killer cells. Studies on humans showed that Salacia reticulata extract changes the composition of intestine microbiota in a favorable manner and shifts it to younger phenotypes and up-regulates IFN-induced genes.
In cosmetics, Kothala Himbutu (INCI: Salacia Reticulata Root Extract) could be used in anti-cellulite and slimming products.
Whitania somnifera
Winter cherry, also called Ashwagangda or Indian ginseng, has sleep-inducing and regulating effects and supports the proliferation of T-lymphocytes and T-killer cells. The Ayurveda medicinal plant is also known because of its anti-inflammatory effects and as an adaptogen. The root extracts are used as antioxidants.
In cosmetics, winter cherry (INCI: Whitania Somnifera Root Extract) is used in regeneration and nourishing creams, anti-aging products for face and body.
Cosmetics for skin’s immune system
Caring for skin is essential to support skin’s immune system. Skin needs well-balanced moisturizing care, must not be over-stressed by UV rays, its pH balance may not be disturbed by cleansing, instead it barrier should be fortified.
In addition to the plants named before, ginger (Zingiber officinale) or long pepper (Piper longum) and many other traditional medicinal plants have antimicrobial and anti-inflammatory properties and can be efficient players for skin’s immune systems. Their immunological working mechanisms are scientifically discovered and explained in more and more details.
As active ingredients in cosmetics products, such plant extracts can exert positive effects on skin’s immune system.