Homosalate
In plain terms
A UVB chemical sunscreen filter. The body absorbs a lot of it and it lingers, and lab studies tie it to hormone activity strong enough that Europe sharply cut how much is allowed. A mineral filter sidesteps both issues.
What the evidence shows
Homosalate is a UVB chemical filter, and two findings push it onto the avoid side. The first is how much of it the body takes in. In the FDA's absorption study, homosalate reached some of the highest blood levels of any sunscreen filter and lingered: nearly everyone exceeded the threshold that triggers further safety review within hours, and all participants were still above it a day later. The second is hormone activity. In cell studies it interacts with estrogen, androgen, and progesterone signaling and affects thyroid cells, and Europe's safety committee took this seriously enough to act. After first finding it not safe at the long-standing 10% level, the committee cut the allowed amount to 7.34% and only in face products, effective in 2025; for everything else the safe level it set was a small fraction of a percent. The United States still permits homosalate at up to 15%, so where you shop decides your exposure. None of this is proven harm in people, and the hormone evidence is mostly laboratory cell work, so the concern rests on absorption and mechanism. But it is a heavily absorbed filter that a major regulator restricted over hormone concerns, and zinc oxide and titanium dioxide cover the same UVB rays without either question. The cautious choice is the mineral one: switching filters, not skipping sun protection.
On the label
Listed as homosalate. The US still permits it up to 15%, far above Europe's limits, so the label is where you catch it. Zinc oxide and titanium dioxide give UVB protection without the hormone or absorption questions; this is about choosing a different filter, not skipping sun protection.