Chemical and physical sunscreens: differences and which one to choose

When choosing a sunscreen, even before SPF, there is a question that causes confusion: are chemical filters or physical filters better? Simplifications and outright myths circulate around this topic — starting with the idea that mineral filters “reflect” rays like a mirror. In this entry of our glossary, we look at how the two filter families really work, the pros and cons of each, and how to choose based on your skin type.

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What Are Sunscreen Filters?

Sunscreen filters (or UV filters) are the ingredients that enable a sunscreen to protect the skin from ultraviolet radiation: UVB, responsible for sunburn and direct damage to cellular DNA, and UVA, which penetrate more deeply and are the main cause of photoaging and pigmentation. In Europe, the filters permitted in cosmetics are listed in Annex VI of Regulation (EC) 1223/2009: only molecules assessed as safe by the Scientific Committee on Consumer Safety (SCCS), within defined maximum concentrations, may be used in a formula.

The two main families are organic filters, commonly called “chemical” filters, and inorganic filters, called “physical” or “mineral” filters. The distinction in the names is more commercial than scientific — mineral filters are also, in every respect, chemical substances — but this is now the terminology we all know.

This has a practical consequence worth keeping in mind: a claimed level of protection comes from authorized filters, formulation, the amount applied, and standardized testing. This is why the “natural” alternatives that periodically circulate — the latest being beef tallow used instead of SPF — are not mild protections: they are unknown protections. A shiny film on the skin is not a shield.

Chemical (Organic) Filters: How They Work

Chemical filters are organic molecules that absorb UV radiation: they capture the photon’s energy and convert it into a very small amount of heat, releasing it in a harmless form. Among the most widely used in Europe are INCI names such as Ethylhexyl Triazone, Bis-Ethylhexyloxyphenol Methoxyphenyl Triazine, Methylene Bis-Benzotriazolyl Tetramethylbutylphenol (which also behaves partly as a physical filter), and Diethylamino Hydroxybenzoyl Hexyl Benzoate.

Their strengths are clear:

• Lightweight, transparent textures: they spread easily, leave no white cast, and are well suited to fluid formulas, ideal for daily use on the face.
• Broad-spectrum protection: newer-generation filters cover UVA and UVB very efficiently and are highly photostable.
• High protection with relatively low concentrations, which improves the formula’s cosmetic elegance.

The traditional limitation of chemical filters is tolerability: some older-generation molecules (such as Oxybenzone, now used less and less) could cause sensitization on reactive skin. Modern filters are much more stable and better tolerated, but caution is still essential when the skin is compromised or dermatitis is active.

Physical (Mineral) Filters: How They Really Work

There are two physical filters: Titanium Dioxide and Zinc Oxide. They are mineral powders that remain on the skin’s surface and protect primarily... by also absorbing UV radiation.

Let’s debunk the myth: contrary to what is often claimed, mineral filters do not work by “reflecting rays like a mirror.” Photochemistry studies have shown that Titanium Dioxide and Zinc Oxide absorb approximately 95% of the UV radiation they block, reflecting or scattering only a small portion, mostly in the visible-light spectrum — which is why they leave a white cast on the skin.

The benefits of mineral filters:

• Excellent tolerability: because they are inert and do not penetrate healthy skin, they are the first choice for sensitive or reactive skin, children, and skin after dermatological treatments.
• Photostability: they do not degrade with sun exposure.
• Immediate effectiveness after application.

The disadvantages are mainly cosmetic: the white cast (reduced but not eliminated by micronized forms), denser textures, and some difficulty achieving very high SPF without making the formula feel heavy. To limit the white cast, the industry uses nanoparticle forms, indicated in the INCI by the word nano in square brackets immediately after the ingredient name: on intact skin they remain on the surface and are considered safe by the SCCS under the approved conditions of use, while inhalation is discouraged (so take care with mineral-based spray formats).

Chemical or Physical: The Differences at a Glance

Placed side by side, the two families differ as follows:

1. Mechanism: both absorb UV radiation; minerals also diffuse a small portion of it. The real difference is not “absorption versus reflection,” but the nature of the molecules.
2. Texture: chemical formulas are lighter and invisible, while mineral formulas are thicker and more prone to leaving a white cast.
3. Tolerability: highest for minerals; very good for newer-generation chemical filters, with a little more caution needed for reactive or damaged skin.
4. Protection range: today, the best results are often achieved by combining several filters, including filters from both families, to cover the entire UVA and UVB spectrum in a photostable way.

Which One to Choose Based on Your Skin Type

There is no absolute winner: there is the right filter for the right skin. Here are some practical guidelines:

• Sensitive, reactive skin, with couperose or dermatitis: prioritize mineral filters or formulas with the latest-generation chemical filters tested for sensitive skin, and look for soothing ingredients such as thermal water and ceramides.
• Oily or acne-prone skin: the priority is a lightweight, non-comedogenic, sebum-absorbing texture; modern chemical filters in fluid or gel vehicles are generally the most comfortable choice. Do not skip protection: this is precisely what triggers the worsening of acne at the end of summer.
• Skin with pigmentation or discoloration: you need a broad-spectrum SPF 50 all year round, preferably with antioxidants (such as Vitamin C) that also counteract UV-induced oxidative stress. Once pigmentation has appeared, the choice of filter matters even more: we discuss this in our guide to sunspots on the face.
• Children and damaged skin: mineral filters in cream form, avoiding sprays.

For those looking for daily anti-pigmentation protection, our facial sunscreen combines broad-spectrum UV filters, encapsulated Vitamin C, and probiotic ferments in a lightweight texture that can also be used under makeup.

And to solve everyone’s real problem — reapplication every two hours — there is the pocket-sized format, smaller than a credit card, to keep in your handbag or wallet at all times.

Remember: the best filter in the world will not work if applied in insufficient quantities. For the face, you need approximately two finger lengths of product, reapplied every two hours of exposure and after every swim, regardless of which filter family you choose.

After-Sun Care and Reactivity: The Rest of the Team

Protection is only half the work in summer: after exposure, the skin needs to be rehydrated and soothed. A mineral-rich thermal water spray helps calm redness and strengthen the skin barrier after a day in the sun.

For more information, also read our guide to choosing the best sunscreen for every skin type, our advice on what to apply to sensitive skin after sun exposure, and our in-depth look at the relationship between sun protection and vitamin D.

In Summary

Chemical and physical filters achieve the same goal through slightly different means: the former absorb UV rays with organic molecules in lightweight, invisible textures, while the latter use inert minerals with excellent tolerability. Modern formulas often combine them to offer the best of both. More than the filter family, three things matter: broad-spectrum UVA/UVB protection, the correct amount, and consistent reapplication. In the end, the perfect sunscreen is the one you actually use every day.

You can also find LeLang products in our partner pharmacies throughout Italy, where a pharmacist can help you choose the right filter for your skin.

On the website: how to choose sunscreen · the beef tallow case · sunspots on the face · sun protection and vitamin D