Using sunscreen is one of the simplest things we can do to take care of our skin, yet it is still one of the most underrated. Many people only apply it on holiday, only when the sun is strong, or only when they remember to do so. Others choose it at random, looking at the SPF number without really knowing what’s behind that acronym or what ingredients they’re putting on their skin.
And when it comes to sunscreens — mineral or chemical — the confusion grows. What’s the difference? Is one safer than the other? Are they bad for the sea? These are legitimate questions, which many ask themselves but which rarely find a clear answer. Yet understanding how what we apply every day works, especially in summer, is the first step to doing it right.
Sunscreens may be different but they all have the same objective: to protect the skin from ultraviolet rays (UVA and UVB), responsible for sunburn, premature skin aging and increased risk of skin cancer. In Europe, there are around thirty UV filters authorized in cosmetics and they are used in different combinations to guarantee broad-spectrum protection.
The main difference between mineral filters (also called physical) and chemical filters (also called organic) concerns their mechanism of action.
Mineral filters
Mineral filters mainly act as a sort of “screen” positioned on the skin surface. The two most used are zinc oxide and titanium dioxide, substances of natural origin with a long history of use in dermatology and cosmetics.
They are often defined as “physical” filters because they act mainly on the skin surface. Once applied, they form a film on the skin which helps to reflect, diffuse and absorb UV radiation, reducing its penetration into the skin layers. They therefore remain mainly on the surface of the skin and do not show significant systemic absorption under normal conditions of use. Furthermore, the protection is active from the moment of application, without the need to wait.
All this makes them particularly suitable for sensitive, reactive or redness-prone skin, but also for children, so they are often preferred precisely because of their tolerability.
However, an important aspect concerns the formulation: titanium dioxide is often used in nanometric form, i.e. with very small particles, to make the creams more transparent and pleasant to apply. The “non-nano” versions, with larger particles, tend to leave a more visible whitish film, an effect that many find unpleasant, especially on medium or dark skin tones.
Nanoparticles therefore improve the aesthetics of the product, but do they present any risks? Their safety has been extensively evaluated at European level and authorized within strict limits in cosmetics. The scientific discussions mainly concern specific conditions of exposure and particular forms of use, rather than the use in sun filters applied to intact skin.
Chemical filters
Chemical filters work completely differently: they do not reflect UV rays, but absorb them. The organic molecules contained in the formula intercept the energy of the sun’s rays and convert it into a less harmful form, generally heat, which is then dispersed by the skin. It is an active mechanism, which requires a direct interaction between the filter molecules and solar radiation.
There are numerous authorized chemical filters, each with different characteristics: some protect mainly from UVB (responsible for sunburn), others from UVA (which penetrate deeper and are associated with skin aging), still others offer coverage on both spectrums. For this reason, modern formulations tend to combine multiple chemical filters together, in order to achieve truly broad-spectrum protection.
A practical aspect that should not be overlooked is the activation time: many creams with chemical filters need to be applied approximately 20–30 minutes before exposure to the sun. This is because the molecules must be evenly distributed on the skin and bind to the surface layers in order to function best. Applying them at the last second, just before diving into the water, means exposing yourself to reduced protection.
From a cosmetic point of view, however, chemical filters offer an important advantage: they tend to give lighter, more fluid and transparent formulas, easily absorbable and invisible on the skin. For this reason they are often preferred by those with oily skin, by those who use sunscreen under daily make-up, or simply by those who can’t stand the sensation of “thick cream” on their face.
But are they dangerous to your health? Some studies have found that certain chemical sunscreens can be absorbed in small quantities by the body, but regulatory authorities consider these ingredients safe under intended conditions of use and the evidence on endocrine effects is inconclusive.
Which filter category is better?
There is no absolute “best” filter. Both types undergo rigorous safety evaluations and tests before being authorized in cosmetics on the market – in Europe the regulations are particularly stringent – and neither is intrinsically superior to the other in terms of protection.
Modern cosmetic research, moreover, has already overcome the logic of comparison: many formulations on the market today combine mineral and chemical filters together, exploiting the strengths of both. The minerals guarantee immediate and stable coverage, the chemicals complete the protection spectrum and improve the texture of the product. The result is a more balanced, effective and pleasant to use formula.
But there is one factor that matters more than all the others, and which is often underestimated: the way in which the cream is applied. Even the best sunscreen in the world protects little if it is applied in insufficient quantities, not reapplied after swimming or sweating, or chosen without considering the needs of your skin.
In other words, the best sunscreen isn’t the one with the most sophisticated ingredients: it’s the one you actually use, in the right amount and with the right consistency.
Attention to the marine environment
In recent years the issue of the impact of sunscreens on marine ecosystems has gained more and more attention, both in the scientific community and in public debate. And not without reason. Some substances present in chemical filters, in particular oxybenzone and octinoxate, have been associated with negative effects on corals and marine biodiversity (interference with reproduction, coral bleaching, toxicity for some aquatic species).
Concern has become such that some areas of the world — Hawaii was among the first, followed by other tropical destinations — have introduced legislative restrictions on these ingredients in sunscreen products sold or used there.
However, the issue is more complex: several studies indicate that not only some chemical filters, but also mineral filters and other components of cosmetic formulas can contribute to the environmental impact. The release of large quantities of solar products into the sea remains a factor to be considered in general.
And individual behaviors also make a difference: avoiding applying large quantities of cream just before entering the water, choosing water-resistant products to reduce dispersion, and waiting for the product to be absorbed before diving are small measures which, multiplied across millions of people, can have a real impact.
Sources: Echa / European Commission / FDA
