Products
Sunscreens are preparations for external use that contain UV filters (sunscreen filters) as active ingredients. They are available as creams, lotions, milks, gels, fluids, foams, sprays, oils, lip balms and fat sticks, among others. These are generally cosmetics. In some countries, sunscreens are also approved as medicines. Which filters are approved varies from country to country. Sunscreens were first developed in the late 19th and early 20th centuries. The first known commercial products, such as Ambre Solaire and Piz Buin, were launched in the 1930s and 1940s, respectively.
Structure and properties
A distinction is made between organic and inorganic UV filters. Because one substance does not cover the entire spectrum, several filters are combined to achieve the necessary protection. Examples of organic (“chemical”) filters (selection):
- Anisotriazine
- Avobenzone (butylmethoxydibenzoylmethane)
- Benzophenone-3, benzophenone-4, benzophenone-5
- 3-benzylidenecamphor
- Bisimidazylate
- Diethylaminohydroxybenzoylhexyl benzoate
- Drometrizole trisiloxane
- Ethylhexyl methoxycinnamate
- Ethylhexyl triazone
- Octocrylene
Examples of inorganic (“physical”, mineral) filters:
- Titanium dioxide (TiO2)
- Zinc oxide (ZnO)
By the way, the name of physical filters is not quite correct, because the inorganic filters are also chemical compounds. The organic filters are benzophenones, anthranilates, dibenzoylmethanes, PABA derivatives, salicylates, cinnamic acid esters and camphor derivatives. The active ingredients are incorporated into different bases that determine the product’s properties. Additional antioxidants are often included as adjuvants. They are intended to counteract the damage caused by UV rays in the skin.
Effects
Sunscreen filters absorb, reflect and scatter UV radiation, preventing its harmful effects on the skin, cells, connective tissue and genetic material. They are effective only against UV-A (320-400 nm) or UV-B (290-320 nm) or against both types of radiation. The filters can convert the UV radiation into harmless heat, for example. The sun protection factor (SPF “factor 30”, “factor 50”), which is indicated on the packaging of the products, refers to UV-B radiation. It indicates how much longer you can stay in the sun before redness develops. A self-protection period of 10 minutes can be extended to 300 minutes with a factor of 30. In English, the SPF is called SPF (Sun Protection Factor). However, to achieve this factor, a great deal of sunscreen must be applied. Studies have shown that this is unrealistic in practice. Therefore, the specified sun protection factor is hardly ever achieved.
Areas of application
To protect the skin from sun and UV radiation. To prevent sunburn, premature aging of the skin, age spots and skin diseases associated with radiation:
- Melanoma
- Actinic keratosis
- Basal cell carcinoma
- Spinalioma
Dosage
According to the instructions for use. Sufficient sunscreen should be used and the agent should be applied evenly and as far as possible without gaps. The agents should be used before sun exposure. Sunscreens can discolor textiles. Therefore, they should be well absorbed. Sunscreens have limited water resistance. A lot of protection is lost not only when sweating and bathing, but also when drying the skin with a cloth. Therefore, the products should usually be applied several times to maintain the effect. However, the total protection time cannot be extended by this. The shelf life of the products is limited. After opening, they may usually be used during about one year.
Precautions
- Do not apply in case of hypersensitivity.
- Avoid contact with the eyes.
- Use age-appropriate products.
- Sunscreens do not provide absolute protection from UV radiation.
Adverse effects
Sunscreens can cause local skin reactions, skin irritation and allergic reactions.The inorganic filters zinc oxide and titanium dioxide can lead to a white coloration of the skin and dry it out somewhat. The finer the particles are in the product, the less pronounced this effect is. With modern products, the so-called “whitening effect” is practically absent. The organic sunscreen filters are not without controversy, because effects on the hormone system have been shown in laboratory and animal tests (endocrine disruptors). However, the authorities rate them as safe. Some substances can also be photoinstable, i.e. they can decompose under UV radiation (e.g. avobenzone, dibenzoylmethanes). The inorganic filters are photostable.