Mineral or chemical sunscreen

Zinc oxide or organic filters? How the two types of sunscreen work, what the studies on absorption mean, and how to choose one you will use daily.

Why the question matters

UV radiation is the most important external factor in visible skin aging, and daily sunscreen is the most effective preventive step against it (see UV radiation and photo-aging). Choosing a sunscreen has become complicated: “mineral”, “chemical”, “clean”, “reef-safe”. This article sorts out what the terms mean and what the evidence says.

Two types of filters

The terms “mineral” and “chemical” are imprecise, because all filters are chemicals. More accurate are inorganic and organic filters.

	Mineral (inorganic)	Chemical (organic)
Examples	Zinc oxide, titanium dioxide	Avobenzone, octocrylene, newer filters such as bemotrizinol or bisoctrizole
How they work	Mainly absorb UV, partly scatter and reflect it	Absorb UV and convert it into small amounts of heat
UV range	Zinc oxide covers UVB and much of UVA	Combinations needed for broad protection
Texture	Can leave a white cast, often thicker	Usually lighter and invisible
Skin tolerance	Very rarely irritating	Well tolerated by most; rare allergies to individual filters

A common misconception is that mineral filters work only by reflection like a mirror. Studies show that zinc oxide and titanium dioxide also largely absorb UV radiation. The practical difference is smaller than marketing suggests.

What the absorption studies mean

In 2019 and 2020, two randomized studies by the US Food and Drug Administration (Matta and colleagues, JAMA) showed that several organic filters, including avobenzone, oxybenzone and octocrylene, are absorbed into the blood at concentrations above a threshold at which the FDA requires further safety studies. The authors explicitly stated that this does not mean the filters are unsafe, and that people should continue to use sunscreen. The threshold triggers further safety testing and says nothing about toxicity on its own.

In the EU, UV filters are regulated as part of cosmetics law, and each permitted filter has a maximum concentration. In 2022, the EU tightened the limits for benzophenone-3 (oxybenzone) and octocrylene (Commission Regulation (EU) 2022/1176), citing possible hormonal effects. Many EU sunscreens use newer filters that are absorbed very little because of their large molecules. Mineral filters in nano form are permitted in the EU under specific conditions after a scientific safety assessment.

Choosing by skin type

Sensitive or reactive skin, rosacea, after treatments: mineral filters are often better tolerated, because contact allergies to them are practically unknown.
Pigmentation and melasma: visible light can also worsen pigmentation. Tinted sunscreens with iron oxides offer additional protection against visible light; a randomized study in melasma patients (Castanedo-Cazares and colleagues, 2014) supported this.
Darker skin tones: modern organic or hybrid formulations avoid the white cast that makes many mineral products impractical.
Sport and water: water-resistant formulations of either type, reapplied after swimming and towelling.

The most important factor: the amount

The SPF on the label is measured with 2 mg of sunscreen per square centimeter. Most people apply much less, which reduces the actual protection considerably. For the face, this means about half a teaspoon, applied every morning and reapplied after hours in direct sun. A sunscreen you enjoy using every day protects better than a theoretically superior one that stays in the drawer. How sunscreen fits into a full routine is described in The evidence-based skincare routine.

Sunscreen and skin treatments

After treatments that stimulate skin renewal, such as microneedling or polynucleotides, the skin is temporarily more sensitive. Consistent sun protection is part of the aftercare, both to avoid irritation and to protect newly formed collagen from UV-driven breakdown. In the first days after a treatment, a mineral sunscreen is often the gentler choice. Your physician will give specific advice after each treatment.

References

Hughes MC, Williams GM, Baker P, et al. Sunscreen and prevention of skin aging: a randomized trial. Ann Intern Med. 2013;158(11):781-790. PMID 23732711.
Schneider SL, Lim HW. A review of inorganic UV filters zinc oxide and titanium dioxide. Photodermatol Photoimmunol Photomed. 2019;35(6):442-446. PMID 30444533.
Cole C, Shyr T, Ou-Yang H. Metal oxide sunscreens protect skin by absorption, not by reflection or scattering. Photodermatol Photoimmunol Photomed. 2016;32(1):5-10. PMID 26431814.
Matta MK, Zusterzeel R, Pilli NR, et al. Effect of Sunscreen Application Under Maximal Use Conditions on Plasma Concentration of Sunscreen Active Ingredients: A Randomized Clinical Trial. JAMA. 2019;321(21):2082-2091. PMID 31058986.
Matta MK, Florian J, Zusterzeel R, et al. Effect of Sunscreen Application on Plasma Concentration of Sunscreen Active Ingredients: A Randomized Clinical Trial. JAMA. 2020;323(3):256-267. PMID 31961417.
Ekstein SF, Hylwa S. Sunscreens: A Review of UV Filters and Their Allergic Potential. Dermatitis. 2023;34(3):176-190. PMID 36279254.
Mahmoud BH, Ruvolo E, Hexsel CL, et al. Impact of long-wavelength UVA and visible light on melanocompetent skin. J Invest Dermatol. 2010;130(8):2092-2097. PMID 20410914.
Castanedo-Cazares JP, Hernandez-Blanco D, Carlos-Ortega B, et al. Near-visible light and UV photoprotection in the treatment of melasma: a double-blind randomized trial. Photodermatol Photoimmunol Photomed. 2014;30(1):35-42. PMID 24313385.
Petersen B, Wulf HC. Application of sunscreen--theory and reality. Photodermatol Photoimmunol Photomed. 2014;30(2-3):96-101. PMID 24313722.