Chemical vs mineral sunscreen — what the filters actually do.

Chemical and mineral sunscreens both provide effective UV protection when properly formulated and applied. The distinction between them is not primarily about safety — both are regulated, well-studied, and appropriate for daily use in the vast majority of people. The distinction is about mechanism, cosmetic experience, and specific use cases where one outperforms the other.

How chemical filters work

Chemical UV filters — also called organic filters — absorb UV radiation. When a UV photon strikes a chemical filter molecule, the molecule enters an excited energy state and releases that energy as heat. The filter is consumed in this process: the molecules become less effective as they absorb more UV over time, which is why reapplication is necessary for sustained protection.

Common chemical filters and what they cover:

Avobenzone. The primary UVA filter in most Western formulations. It absorbs across a broad range of UVA wavelengths, but it is photounstable — it degrades under UV exposure faster than most other filters. Modern formulations pair it with photostabilisers (octocrylene, Tinosorb S, Escalol 517) to extend its effective life.

Tinosorb S and Tinosorb M. European-approved broad-spectrum filters (UVA + UVB) that are photostable and among the most effective filters available. Widely used in European, Japanese, and Australian formulations; not yet FDA-approved in the US, which limits availability of the most photostable chemical sunscreens in American-market products.

Octinoxate (octyl methoxycinnamate). A UVB filter. Common in older formulations; increasingly being replaced by more photostable alternatives. It does not provide UVA protection and has raised environmental concerns relating to coral reef toxicity.

Oxybenzone. A UVB filter with some UVA coverage. Effective but one of the more studied filters from a sensitisation standpoint — contact allergy rates are measurably higher than for other filters, though still low in absolute terms. Also flagged in the coral reef toxicity discussion.

Mexoryl SX/XL. UVA filters used in some European and Canadian brands. Photostable, effective, well-tolerated. Less commonly found globally.

How mineral filters work

Mineral filters — zinc oxide and titanium dioxide — work by scattering and reflecting UV radiation rather than absorbing it. The mechanism is physical rather than chemical.

Zinc oxide. Provides broad-spectrum coverage — both UVA and UVB — from a single ingredient. Photostable: it does not degrade under UV exposure, so its protective capacity does not diminish over time in the same way chemical filters do. Highly tolerated; sensitisation is very rare. The main cosmetic limitation is a white cast on medium to deep skin tones (addressed by micronisation, encapsulation, and iron oxide tinting in better formulations).

Titanium dioxide. Primarily a UVB filter with limited UVA coverage. Often paired with zinc oxide in mineral formulations to improve the UVA component. Less prone to white cast than zinc oxide alone at equivalent concentrations, but provides less complete UVA protection as a standalone filter.

Photostability — the practical difference

The photostability difference has real practical consequences. Chemical filters degrade under UV exposure; mineral filters do not. This means that chemical sunscreens require more consistent reapplication to maintain their labelled SPF, and that older chemical formulations (containing unstabilised avobenzone) may perform well below their labelled value after extended outdoor use.

Modern European and Australian chemical formulations using Tinosorb S are significantly more photostable than older US-market chemical sunscreens. The formulation matters as much as the filter type.

Which to choose

For daily urban use with limited direct sun: either works. Compliance is the most important variable — the best sunscreen is the one worn consistently. A lightweight chemical sunscreen with no white cast often achieves better compliance than a mineral formula that leaves a noticeable cast.

For extended outdoor use or high-UV conditions: a photostable formula — either a modern chemical sunscreen with Tinosorb, or a mineral zinc oxide formula — is preferable. Both maintain their protection more reliably under sustained UV exposure than older chemical formulations.

For reactive, sensitised, or compromised skin: mineral zinc oxide is the first choice. It sits on the skin surface rather than being absorbed, and sensitisation rates are very low. Chemical filters, particularly oxybenzone and some fragrant formulations, carry a higher sensitisation potential for reactive skin.

For hyperpigmentation or melasma: a tinted mineral sunscreen containing iron oxide. Iron oxide protects against visible light — which UV ratings do not measure — and visible light independently stimulates melanin production. An untinted sunscreen, chemical or mineral, does not address this trigger.

For darker skin tones: chemical broad-spectrum sunscreens eliminate the white cast problem entirely. Tinted mineral formulations in a range of shades address it for those who prefer mineral filters.

Safety questions

Several chemical filters have been studied for systemic absorption — they can be detected in blood, urine, and breast milk after application. The FDA requested further safety data on several chemical filters in 2019 for this reason. This does not mean they are unsafe at current usage levels: absorption does not equal harm, and no established adverse health effects in humans have been documented at concentrations encountered through normal sunscreen use. The established harm from UV exposure — skin cancer, photoageing — is well-documented; the theoretical risks of filter absorption at sunscreen application levels are not.

Both mineral and chemical filters have favourable safety profiles for the vast majority of users in typical daily use.

The Lux & Glo position

Sunscreen is not part of the three-step ritual — it precedes it. The choice between chemical and mineral sunscreen is personal, and both categories contain well-formulated, effective options. Understanding the mechanism and photostability of each filter makes the decision clearer than the marketing typically allows.

The most important variable remains application: adequate quantity (approximately half a teaspoon for the face and neck), consistent daily use, and reapplication when relevant.