Solar filters. Effectiveness, safety and protection

Benefits of solar products versus their potential health and environmental risks.

Sunscreens are essential to protect against ageing or to reduce the risk of diseases such as skin cancer. However, the risk and safety of solar products is increasingly a cause for concern.

Despite the efforts made to improve the quality of sunscreens, questions have been raised about the legal status of UVB filters such as Ethylhexyl methoxycinnamate and octocrylene. Research has highlighted their harmful effects on the environment and as potential endocrine disruptors. Controversially, some filters such as PABA and benzophenones are associated with photoallergic skin reactions.

Sunscreens containing titanium oxide and zinc oxide are accepted as ‘safe’. Particle size must also be taken into account: marine toxicity studies have concluded that nano-sized ZnO causes coral bleaching and titanium dioxide harms marine fauna.

Classification of solar radiation

Sunscreens are topical cosmetic products intended to prevent or diminish the effects caused by solar radiation on the skin such as sunburn or ageing through their ability to absorb, reflect and scatter UV rays.

The solar spectrum is referred to using different names depending on the wavelength of the radiation:

  • Ultraviolet C. These are very dangerous radiations, but they are absorbed by the ozone layer and do not reach the earth’s surface.
  • Ultraviolet B. They are the main cause of skin cancer.
  • Ultraviolet A. These are the radiations that emit the most energy and are responsible for tanning and skin ageing.
  • Visible radiation. Makes it possible to perceive colours.
  • Infrared radiation. Produces calorific effect and vasodilatation. Penetrates to the hypodermis.

Sunscreens contain active ingredients known as solar filters:

  • organic filters
  • inorganic filters
  • biological or hybrid filters

Organic filters

Organic filters act by absorbing ultraviolet solar radiation. They capture incident energy and re-emit it again as thermal radiation, harmless to the skin. Depending on the absorbed radiation, a distinction is made between UVB, UVA and broad-spectrum filters. All of them require about thirty minutes to carry out this action and must be applied with due notice. Organic filters are classified according to the radiation they absorb.

There are selective filters for:

  • UVB radiation
    • Salicylates
    • Cinnamates
    • Octocrylene
    • Phenylbenzimidazole sulfonic acid
  • UVA radiation
    • Benzophenones
    • Butyl Methoxydibenzoylmethane
    • Terephthalylidene Dicamphor Sulfonic Acid

Broad-spectrum filters (UVA and UVB)

In recent years, new filters that absorb, reflect and scatter light are emerging as a hybrid between mineral and chemical filters. They have been created to avoid the issues raised by the old chemical filters. They are larger in size, are not absorbed, are low in allergens and are safe so far.

  • Methylene bis-benzotriazolyl tetramethylbutylphenol
  • Bis-Ethylhexyloxyphenol Methoxyphenyl Triazine
  • Diethylhexyl butamido triazone

Inorganic filters

Its action is due to its ability to deflect, reflect and/or scatter incoming light without any chemical interaction between the solar filter and any component of the radiation. The protective action by simple shielding effect makes them effective over the entire solar spectrum, which is why they are commonly known as sunscreens.

This group includes talc, zinc oxide, titanium dioxide, iron mica-oxide, mica-titanium, silicates, inorganic and inert pigments, and pigments opaque to solar radiation. Their low reactivity and therefore low sensitisation reactions make them particularly suitable for preparations for children.

Biological filters

They promote an antioxidant effect based on the sequestration of free radicals responsible for skin ageing and photo-induced cancer. They act by filtering part of the incoming solar radiation and neutralising the aggressive local effects of radiation, or even by stimulating the skin’s immune system.

In addition to contributing to the photoprotective activity of physical and chemical filters, they improve the appearance and elasticity of the skin and boost the skin’s immune subsystem.

Challenge: Safer solar filters and increased awareness

A major challenge facing the cosmetic industry is the development of increasingly safe and environmentally-friendly sunscreens. With solar filters that do not absorb into the skin, have no hormonal or toxic effects, are photostable, do not cause allergic reactions, are biodegradable and have no effect on marine flora and fauna.

The proper use of sunscreens helps to combat the risks associated with sun exposure, without forgetting that, to date, the benefits of sunscreen use outweigh the possible risks.

Therefore, from the cosmetic industry, we must continue to raise awareness and inform society of the different types of sunscreens available, as well as their correct use for the health and protection of your skin and the planet.

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