Most conventional sunscreens contain oxybenzone, octinoxate, avobenzone and homosalate. These chemical filters absorb UV radiation by undergoing a photochemical reaction in the skin. That reaction requires the chemicals to penetrate the skin, which means they enter the bloodstream. The FDA found oxybenzone in blood at concentrations exceeding its own threshold for systemic exposure after a single day of full-body application. That was in 2019. The agency has not updated its sunscreen safety standards since.
What is in conventional sunscreen
The six most common chemical UV filters in the US are oxybenzone, octinoxate, avobenzone, homosalate, octisalate and octocrylene. All six are absorbed through the skin and detectable in blood, urine and breast milk. Oxybenzone is the most studied and the most concerning: it is found in the urine of 97% of Americans, according to CDC biomonitoring data. It is chemically similar to oestradiol and binds to oestrogen receptors. The European Union restricts oxybenzone to 2.2% concentration in sunscreens. The US has no equivalent restriction.
Oxybenzone and hormones
A 2004 study in Environmental Health Perspectives found oxybenzone detectable in the urine of all 30 study participants. Subsequent research confirmed systemic absorption and oestrogenic activity at real-world exposure levels. A 2019 study in JAMA found that four common chemical sunscreen filters, including oxybenzone, persisted in the bloodstream for at least 21 days after a single application. Homosalate is an androgen disruptor, shown to block testosterone signalling. Octinoxate has demonstrated thyroid-disrupting effects in animal studies at doses comparable to human exposure.
“The FDA found oxybenzone in blood at concentrations exceeding its threshold for systemic safety after a single day of full-body use. That was in 2019. The standard has not changed.”
PFAS in sunscreen
A 2021 study published in Environmental Science and Technology Letters tested 231 cosmetic products and found PFAS in 56% of foundations, 48% of lip products and a significant proportion of waterproof and long-lasting sunscreens. PFAS are added to personal care products to improve water resistance, texture and longevity. They are not required to be listed on ingredient labels because they are added to the formula as processing aids rather than intentional ingredients. You cannot identify PFAS in a sunscreen by reading the label.
Mineral sunscreen: how it works differently
Mineral sunscreens use zinc oxide or titanium dioxide as UV filters. These mineral particles sit on top of the skin and physically scatter and reflect UV radiation rather than absorbing it through a chemical reaction. Because they do not need to penetrate the skin to function, systemic absorption is minimal. Non-nano zinc oxide particles are too large to be absorbed through the skin. Both zinc oxide and titanium dioxide are on the FDA's GRASE (Generally Recognised As Safe and Effective) list. Chemical filters are not.
How to switch
Switch to non-nano zinc oxide sunscreen
Non-nano means the zinc oxide particles are large enough that they cannot penetrate the skin. Look for this specifically on the label. Recommended brands: Badger Sport (budget), Thinksport SPF 50 (mid-range), MANDA Organic Sun Paste (premium).
Check your existing sunscreen on EWG
The EWG Skin Deep database rates every sunscreen ingredient. Search your current product and see its hazard score. EWG's annual sunscreen guide lists the best and worst performers.
Prioritise children and frequent users
Children have higher skin-surface-to-body-weight ratios and absorb proportionally more of any topically applied chemical. If you use sunscreen daily or apply it to children regularly, this swap is high priority.