Is sunscreen messing with your fertility and endocrine system?

We’ve all been told time and time again to wear sunscreen—even when it’s not glaringly sunny. So, of course, we dutifully dab on a daily tinted moisturizer with SPF or slather on tons of sunblock at the beach feeling pretty virtuous.

But lately the skin protectant has been provoking a raised eyebrow (or two). About half of SPFs don’t live up to their claims, those that say “water-resistant” are pretty much lying, and now a very serious concern has been discovered by researchers at the University of Copenhagen: commonly used sunscreen filters could be lowering men’s fertility.

(“Filter,” if you haven’t heard that term before, is the technical name for the active sun-protection ingredient in your sunscreen.)

The implication that chemicals meant to lower your risk of skin cancer may also be affecting your broader health and endocrine system is one of those “Are you kidding me?” moments in personal care.

It also raises a huge red flag since these ingredients are used in hundreds of products sold in the US and EU, as the The Breast Cancer Fund and the Environmental Working Group have pointed out.

Just how freaked out should we be about this news? We spoke with Alan B. Copperman, MD, director of reproductive endocrinology and infertility at Mount Sinai Hospital and medical director of Reproductive Medicine Associates of New York, to understand just how concerned we should be when slathering on sun protection—and which sunscreens are safe.

Which sunscreen filters cause health issues?

“Chemicals such as avobenzone, homosalate, octyl salicylate, and oxybenzone (BP-3)—often found in personal-care products, including makeup, moisturizers, and sunscreens—have been found to disrupt sperm cell function and potentially to interfere with male fertility,” explains Dr. Copperman.

These ingredients interfere with the body’s endocrine system by decreasing or increasing (depending on the chemical) the production of hormones, and can have far-reaching effects on the developmental, reproductive, and immune system, Dr. Copperman says.

How exactly does sunscreen lower sperm count?

“Some UV filtering sunscreens mimic the effect of progesterone by activating a calcium ion channel, which could in theory interfere with sperm function,” explains Dr. Copperman.

Progesterone is an important steroid hormone in women that plays a role in the menstrual cycle as well as in implantation and pregnancy. (We’d really like to see a study on this, please.) It’s also important in men, says Dr. Copperman, as it counteracts the effects of estrogen on the male body. Progesterone also plays a pretty key role in the immune system.

What did the study show?

Researchers at the University of Copenhagen tested 29 of the 31 UV filters (approved for use in the U.S. and Europe) by applying them to sperm samples of healthy men. The results? Almost half caused the sperm to stop properly functioning.

Nine of the filters mimicked the effect of progesterone and some interfered with vital sperm functions in vitro. Even so, notes Dr. Copperman, more research is needed regarding their effects on fertility.

What can you do to limit your exposure?

Sadly enough, Dr. Copperman says some exposure to endocrine-disrupting chemicals is inevitable—they’re in almost every household product, pesticide, and the environment. He also says not to panic.

Still, “it’s important to pay attention to news articles, become educated, and read labels,” says Dr. Copperman. “Sunscreen can help to prevent skin cancer, and should be used in conjunction with protective clothing including hats.”

Which sunscreens are safe?

Some good news? Mineral-based sunscreen filters such as zinc oxide and titanium dioxide were not implicated. And we can recommend lots of good ones that we’ve personally tested and that appear on the EWG “best of” list.

Keep meaning to take your summer beauty routine in a non-toxic direction? Check out these amazing 9 natural summer products. And these 11 home cleaning products aren’t filled with scary stuff.