Zinc oxide is a white crystalline powder, which for many years remains one of the most popular components of cosmetics. This popularity is due to the wide range of functional activities of zinc, recognized as one of the most important trace elements in the human body. This chemical element is present in different tissues and organs, including the skin, and is directly involved in more than 200 chemical reactions regulated by enzymes. Experts from the Expertology portal can help you learn more about the properties of zinc oxide and evaluate the effectiveness of this common cosmetic ingredient.
Functions of zinc oxide in cosmetics
The total zinc content of the human body is estimated at about 2 g, of which about 60% is in muscles, about 30% in bones, and 6% in the skin. Deficiency of this trace element in the epidermis leads to a disturbance of the current enzymatic reactions that continually take place in the skin. In this regard, the external and internal characteristics of the epidermis are directly dependent on the content of zinc oxide in the tissues.
The level of this trace element in the body is determined primarily by a person’s diet. Zinc oxide is not water-soluble, so its ability to penetrate deep into the epidermis is limited.However, despite this fact, it is scientifically proven that the application of zinc compounds on the skin can achieve a number of positive cosmetic effects, the most pronounced among them:
antioxidant;
sunscreen;
anti-inflammatory;
anti-pigmentation;
anti-aging;
anti-acne;
antimicrobial;
stabilizing.
The functional activity of zinc oxide in a particular cosmetic product depends on the composition and form of application of the product. Below, let’s analyze in more detail the mechanism of action of zinc oxide in creams, masks and cleansers.
Sunscreen properties of zinc oxide in cosmetics
The sunscreen properties of zinc oxide are well known and have been widely used in cosmetology for many years. The substance is considered a classic example of a broad spectrum physical sunscreen. Zinc oxide is most effective at blocking UV rays in the 340-400 nm range, which provides protection from almost the entire UVA range. It can be used alone as a sunscreen, but more often it is combined with other sunscreens, especially titanium dioxide, in cosmetics.
It’s also worth noting that decreasing the size of ZnO particles increases the potential to block UV rays. This means that when choosing an effective sunscreen, one should also pay attention to the particle size of this component.
Antioxidant activity of zinc in cosmetics
Zinc has scientifically proven antioxidant properties, protecting skin cells from unwanted oxidative changes caused by free radicals.The substance exhibits its antioxidant properties in two ways, directly and indirectly:
Direct effects. In the first case, Zn2+ ions bind to the active center of antioxidant enzymes, enhancing their action. It allows to neutralize free radicals, preserving the integrity of cells and structural proteins of the skin. There is evidence that Zn increases the activity of such antioxidant enzymes as glutathione catalase and superoxide dismutase.
Indirect Action.This mechanism is based on stimulating the production of metallothionein, a protein rich in sulfhydryl groups. As an active antioxidant, metallothionein is able to absorb reactive oxygen species. In addition to its antioxidant properties, this protein substance also cleanses the body of toxins by binding free ions of heavy metals.
In clinical studies, scientists discovered that zinc protects the skin from UV-induced immunosuppression. Simply speaking, zinc ions effectively prevent damage to fibroblasts, lipids and DNA molecules that occurs when exposed to direct sunlight.
It is also important to note that the antioxidant effectiveness of zinc compounds is directly related to their bioavailability. Organic chemicals with complex structures, such as zinc cysteine, have demonstrated much greater antioxidant activity than simpler chemicals, such as zinc oxide. Unscrupulous cosmetic manufacturers often ignore this fact when they promise a powerful protective effect of zinc oxide formulations. This is important to consider when choosing the right cream or mask for your face.
Anti-inflammatory activity
The anti-inflammatory properties of zinc compounds can be seen as a derivative of their antioxidant activity. By suppressing free radicals, such substances help the epidermis to cope faster with the acute phase of the inflammatory process, relieving redness and physical discomfort. Zinc also inhibits the formation of inflammatory mediators, such as nitric oxide, by inhibiting the activity of iNOS (nitric oxide synthase). All these mechanisms of action have been confirmed in animal and human experiments.
Because of these properties, Zn compounds are used to treat a number of skin conditions associated with inflammation.These include:
acne;
Rosacea;
Seborrheic dermatitis;
eczema;
Erosive pustular dermatosis;
Wounds of various etiologies.
In addition, zinc-containing chemicals can be used in the treatment of hair diseases (alopecia) and pathological conditions of the mucous membranes (red squamous lichen). Local application of zinc oxide and zinc sulfate paste has also been found to be effective in treating diaper dermatitis and hand eczema.
Anti-pigment protection
Products containing zinc oxide and more complex organic compounds have the potential to combat skin hyperpigmentation, which is attributed to their antioxidant and sun protection properties. In addition, topical application of products containing ZnO twice daily for three months has been shown to improve skin conditions with melanoderma. However, it is important to note that most dermatologists believe the maximum concentration of zinc in cosmetic products should not exceed 1%.
Anti-aging properties
The anti-aging properties of zinc compounds are not well understood. However, considering the complex of antioxidant and sun protection activity, it can be argued that regular use of zinc-containing cosmetics helps prevent the premature aging of tissues and the appearance of signs of photoaging. When choosing anti-aging cosmetics, dermatologists recommend that zinc oxide be replaced with another compound from this group, zinc malonate. A recent study involving 21 women showed that an eight-week course of use of 0.1% malonate copper-zinc cream boosts the regeneration of elastic skin fibers. This, in turn, leads to a marked smoothing of wrinkles.
Anti-acne activity
Almost 90-95% of teenagers all over the world face such an unpleasant phenomenon as vulgar acne. These cosmetic defects can occur in response to the activity of certain bacteria, inflammation, excessive sebum formation and keratinization of epidermal cells. Zinc compounds have proven anti-acne properties. The use of zinc-containing creams and ointments for acne, helps to reduce inflammation caused by acne and has a damaging effect on the Propionibacterium acne bacteria that cause rashes.
The astringent properties of zinc salts are also useful in the treatment of acne. In dermatological tests, it has been shown that zinc oxide is able to regulate sebum production. Combined with its antimicrobial and anti-inflammatory properties, this makes it an essential component of products designed to care for oily skin prone to acne and rashes. In addition, in the fight against acne, dermatologists recommend using zinc compounds not only in the form of creams and ointments, but also orally, as a dietary supplement.
Features of children’s creams with zinc oxide
Zinc oxide is also a common component in children’s creams and ointments used to treat diaper rash and diaper dermatitis. However, this ingredient in children’s creams raises doubts and concerns among many parents about the substance’s safety for the child’s body.Pediatricians and dermatologists find these concerns unfounded and provide a number of arguments in favor of ZnO in children’s cosmetics:
Research has shown that zinc oxide particles larger than 30 nm are not absorbed by the skin when used in lotions or creams. This means that it does not penetrate the bloodstream, affecting only the baby’s skin.
In combination with other ingredients in children’s creams or powder, zinc oxide has anti-inflammatory and soothing properties, further protecting the delicate baby’s skin from aggressive environmental factors.
Zinc oxide can be used as a safe sunscreen for children. Since the substance is not water-soluble, it protects the skin from UV rays even after swimming in the pool or the sea. In addition, using products containing zinc oxide can provide protection against the sun’s wide range of UVA and UVB rays.
Regular use of baby diaper rash cream containing ZnO helps to eliminate the itching that bothers the baby.
Zinc oxide cream has been proven effective in treating eczema and several other skin conditions in children.
Zinc compounds are widely used in cosmetic formulations as active or auxiliary ingredients in creams, masks, lotions, cleansers and powder. The positive effects on the skin and the complete safety of topical application make zinc oxide an excellent ingredient in both adult and children’s skin care products.
Sources:
Study “Zinc-containing compounds for personal care app
- published in the International Journal of Cosmetic Science
“Zinc Oxide” article from THE SCIENCE SAFETY BEHIND YOUR FAVORITE PRODUCTS
Research article “METALLOTIONEIN: BIOLOGICAL FUNCTIONS”
Article “Is Zinc Oxide Safe for Babies?” online journal Parenting
