Sunscreen: which ingredients should be avoided?

Ultraviolet filters are the pillars of sunscreens: without them, products could not protect skin from the sun and its hazards (photoaging, sunburns, hyperpigmentation, skin cancers...). Two main categories of sunscreen filters: mineral (or physical) filters, such as titanium dioxide and zinc oxide, and organic (or chemical) filters. The latter are the main source of controversy due to their potential impact on human health and the environment.

Among the most debated UV filters are oxybenzone (INCI: Benzophenone-3), octocrylene, homosalate and octinoxate (INCI: Ethylhexyl Methoxycinnamate). These compounds are accused of crossing the skin barrier and reaching the bloodstream. Some studies suggest endocrine disruption, that is, interference with the hormonal system, although data remain debated. In rat studies, octocrylene affected thyroid hormone metabolism. Octinoxate impaired the reproductive system and reduced sperm count in rodents. However, it is hard to draw firm conclusions for humans, as these results are not transferable and the concentrations tested exceed those in sunscreens.

In addition to health concerns, the environmental impact of chemical filters fuels debate. Several studies suggest that certain UV filters, such as octocrylene, octinoxate, oxybenzone, and enzacamene (INCI: 4-Methylbenzylidene Camphor), can disrupt marine life and contribute to the phenomenon of coral bleaching. Some regions, such as Hawaii, have banned their use. Note that this risk extends to zinc oxide nanoparticles, which could alter the symbiosis between corals and zooxanthellae, the unicellular algae essential to their survival.

Criticism of these UV filters does not mean they are banned because existing scientific data are insufficient to assess their risk. Nevertheless, as a precautionary measure, we exclude the sunscreen filters controversial, for their health or environmental effects.

Sunscreens can contain fragrances to enhance the sensory experience and mask the unpleasant odor of certain UV filters. Yet they figure among the leading causes of allergic reactions in cosmetic products, including sunscreens. These reactions appear as redness, swelling, itching, or vesicles. Some fragrance molecules can cause photodermatitis, known as photo-contact allergy. This occurs when the applied substance reacts under UV exposure, triggering a skin response. It may seem surprising to find these compounds in sunscreens, but they serve a fragrance function and not all skin types react to them.

A clinical study illustrated this risk: 24 students took part in a phototest using 6-methylcoumarin (6-MC), a fragrance compound integrated into skincare formulations. After six hours of occlusion on different skin areas with solutions containing 5%, 1%, and 0.1% 6-MC, volunteers were exposed to the minimal erythema dose (MED). The MED is the lowest UV dose needed to cause erythema, that is, skin reddening. Results showed that even at 1% concentration, 6-MC could induce an itchy vesicular reaction, while at 0.1% volunteers displayed redness and moderate swelling. No effect was observed in untreated control areas, confirming the ability of some fragrances to sensitize the skin and trigger photocontact allergies.

Our recommendation : If you have sensitive skin, we recommend choosing a sunscreen without fragrance. Regardless of your skin type, test the product on the inner elbow at first use. Then apply it to your face or body.

As mentioned earlier, mineral sunscreen filters—zinc oxide and titanium dioxide—can occur in nanoparticle form. Nanoparticles offer more uniform, transparent UV protection without the whitening effect attributed to microsized mineral filters. This is not without drawbacks, the nanoparticles and are accused of being able to cross the skin barrier and enter the bloodstream. A 2015 study examined titanium dioxide in nanometric form. The results showed that, on healthy skin, nanoparticles remain on the epidermal surface. When the skin barrier is compromised, as after sunburn or in atopic skin, nanoparticles appear to cross the epidermis and accumulate in the dermis, raising questions about their local and systemic toxicity.

Nanoparticles pose an environmental concern. When rinsed off in the shower or carried into the sea, they disperse into aquatic ecosystems, and some studies have shown that they have a detrimental impact on phytoplankton, which is a fundamental link in the marine food chain. Their accumulation could disrupt ecosystems, affecting biodiversity and ocean health. As noted above, studies have shown that zinc oxide nanoparticles can contribute to coral bleaching.

To avoid nanoparticles, check the INCI list: the “[nano]” label is mandatory. We exclude sunscreen filters in nanoparticle form.

Some sunscreens contain essential oils that provide a natural scent. However, these oils are not always compatible with sun exposure, as they can make the skin more sensitive to UV rays. This applies to citrus essential oils such as bergamot, lemon, sweet orange, or grapefruit, which contain furocoumarins. Applying these oils before sun exposure can cause redness or burns—in other words photodermatitis reactions. However, this view deserves nuance. A recent study used spectrophotometry to evaluate the sun protection factor (SPF) of nine essential oils. The SPF values ranged from 1.2 to 36.4, with an average around 11.1.

Never apply undiluted jasmine essential oil to your skin expecting SPF 30+: essential oils must be diluted with care because they can irritate the skin. These results indicate that a formulator might consider incorporating a photoprotective essential oil into a sunscreen.

Researchers went further: after measuring the SPF of essential oils alone, they assessed their effect when added to a sunscreen. They tested a control formula without essential oil. They enriched the same cream with 0.3%, 0.6%, and 0.9% jasmine oil and repeated the test with lilac oil. The results below show that adding less than 1% essential oil significantly increases SPF, in a dose-dependent manner.

Although certain essential oils may benefit sunscreens, it is inadvisable to add them to a ready-made formula : this may compromise the product’s stability and photoprotective efficacy.

• KLIGMAN A. M. & al. Photocontact allergy to 6-methylcoumarin. Contact Dermatitis (1978).

• CROSERA M. & al. Nanoparticles skin absorption: New aspects for a safety profile evaluation. Regulatory Toxicology and Pharmacology (2015).

• ZHONGHUA C. et al. TiO2 nanoparticles in the marine environment : Physical effects responsible for the toxicity on algae Phaeodactylum tricornutum. Science of the Total Environment (2016).

• SUH S. & al. The banned sunscreen ingredients and their impact on human health: a systematic review. International Journal of Dermatology (2020).

• HUTCHISON J. E. & al. Zinc oxide‑induced changes to sunscreen ingredient efficacy and toxicity under UV irradiation. Photochemical & Photobiological Sciences (2021).

• KEARNS G. & al. Sunscreens: potential hazards to environmental and human health. Frontiers in Marine Science (2024).

• ZITO P. M. & al. Sunscreens and photoprotection. StatPearls (2025).

• HUMAIRA N. & al. Evaluation of sun protection factor (SPF) value of essential oils and its application in sunscreen cream. IOP Conference Series: Earth and Environmental Science (2025).