Zinc oxide
Historical background
Zinc oxide has played an important role in cosmetics and medicine for more than 150 years. For example, its use as a powder base is historically documented. In 1866, the substance replaced arsenic, lead and bismuth salts, which had been used until then and were extremely harmful to health. In addition, the substance is traditionally a coloring agent for painters’ paint. This is the reason for the name “zinc white”, which is still commonly used in the painting trade.
Fields of application and use
The inorganic substance is contained in many creams, skin care products, shake mixtures, baby care products as well as in wound healing and hemorrhoid ointments. It has proved particularly effective in soothing and healing moist and weeping skin conditions (for example, eczema), diaper dermatitis, chapped skin, scratch, abrasion and cut wounds, intertrigo (skin wolf), fungal infections and bacterial infections.
It is even suitable for acne treatment, as the active ingredient slows down the growth of acne-causing bacteria on the one hand, and regulates the skin’s own sebum production on the other.
In addition, it is still found today as a white pigment for coloring in decorative cosmetics. One example is compact face powder.
Zinc oxide as a UV filter
In addition, the substance is very often used as a photostable filter in sun protection products. However, there is one small drawback to this, which most people have experienced. Sun protection products containing zinc oxide can lead to a dull and dry skin feeling as well as to a whitening of the skin. The so-called whitening effect is perceived by most as quite disturbing and unpleasant, since it impairs the appearance, for example, on the beach or during outdoor leisure activities. However, the effect is much less pronounced when zinc oxide nanoparticles are used in the preparations. The size of the particles used for suntan lotions and creams is usually between 20 and 60 nm (nanometers). However, the tiny particles are often coated with silicon or aluminum oxide before being added to the preparations. They then agglomerate into aggregates ranging in size from 200 to about 500 nanometers, preventing them from penetrating the body through the skin. This has been tested several times and in different countries.
In principle, however, the substance is very well tolerated. Even children and people with sensitive skin usually tolerate it without problems. It has the advantage that it does not cause allergies and does not decompose.
Incidentally, it has recently been observed that zinc oxide nanoparticles are also increasingly being used in food packaging as UV absorbers.
Zinc oxide in the positive list of the EU Cosmetics Regulation
Several years ago, the substance was included in Annex VI of the EU Cosmetics Regulation as a nano UV filter. This means that the active ingredient is now approved in both forms (non-nano and nano) for use as a UV filter in cosmetic products with up to 25%. Corresponding preparations already on the market cover virtually the entire UV spectrum: from short-wave UVB to long-wave UVA-I radiation. In the USA, zinc oxide is even one of only two UV filters officially approved by the US Food & Drug Administration for UVA protection in sunscreen products, as its efficacy and safety have been proven. Both the EU Scientific Committee on Consumer Safety (SCCS) and the US Food & Drug Administration conducted extensive studies on the safety of zinc oxide in cosmetics. In order to limit the impact on our environment as much as possible, the concentration of zinc oxide in the preparations is strictly controlled.
The substance is therefore used by the manufacturers in an optimum concentration, which of course complies exactly with the legislator’s specifications. The active ingredient is not used in products that could either be swallowed or inhaled (for example lipsticks or sprays).
How does the UV filter zinc oxide work?
By the way, the mode of action of zinc oxide is quickly explained:
Through the use of the substance, a physical barrier is formed, which in turn ensures that the harmful UV rays can either no longer penetrate to the skin at all or at a much lower intensity. The UV rays are simply reflected and this is a physical protection mechanism – without any chemicals.
In natural cosmetics, zinc oxide has therefore now also a firm place. The active ingredient is used here primarily for sun protection products, but also for wound protection products and baby care.
Sun protection with zinc oxide: a good choice
Time and again, fears have been expressed that very small nanoparticles could reach the basal cell layer within the epidermis and cause damage there.
However, Australian researchers recently found in an elaborate study that zinc oxide nanoparticles can hardly penetrate the skin and therefore do not pose a safety risk. Even after repeated daily or even hourly application, no elevated zinc oxide levels can be detected beyond the horny layer. Instead, the particles remain suspended in the horny layer. The research team led by Doctor Yousuf Mohammed of the University of Brisbane analyzed the distribution of the substance in the skin using fluorescence lifetime microscopy (FLIM) and multiphoton tomography (MPT). In no case could zinc oxide be traced below the stratum corneum. This was true for both the uncoated and coated variants. (Source: https://www.aerztezeitung.de/Medizin/Zinkoxid-Nanopartikel-in-Sonnencreme-offenbar-sicher-254292.html)
Scientists therefore assume, based on current knowledge, that sun creams with zinc oxide nanoparticles cannot trigger any skin damage.
Nevertheless, we, here at Cosmacon, only formulate with the non-nano zinc oxide.
It’s a little coarser (which you can see under a microscope) and it’s a little more tedious to rub in. But many consumers do not accept nano-compounds and therefore we recommend our customers to use only non-nano products.
Also coating with silicone compounds, which would lead to a nicer skin feeling, is taboo for us. In natural cosmetics, we rely on a natural, “coarse” and pure zinc oxide.
Zinc oxide fact sheet
INCI: Zinc Oxide
Molecular formula: ZnO
CAS number: 1314-13-2
Description: a white, loose powder
Solubility: practically insoluble in water
Concentrations of use: 5.0 to a maximum of 25.0 percent
Effect: drying, skin-protecting, astringent, wound-healing, skin-caring and slightly antiseptic properties; possible as sole UV filter up to max. SPF25
Zinc oxide in high-quality cosmetics from Cosmacon
Zinc oxide is a mineral UV filter with very good tolerance and excellent efficacy. According to several extensive studies, it is considered harmless even in its nano-form. The substance is ideal for skin protection and skin care in natural cosmetics. Particularly noteworthy is its use in sun protection products. Let us advise you, we will be happy to inform you in more detail.