In theory, sunscreen is pretty awesome. Made from a mix of organic and inorganic ingredients that reflect harmful UV rays, or absorb them and then convert them into heat, these protective creams, lotions, and sprays shield our skin from radiation that may otherwise leave us with a painful lobster-red tinge.

And because excessive sun exposure has been linked to skin cancer, sun-care products are also key preventive agents when it comes to our health and well-being.

What you may not know, however, is that some of these ingredients—particularly the inorganic ones—may actually be damaging your body from the inside out. These include hormone-disrupting chemicals, allergens, and other irritants that help store-bought sunscreens maintain a certain scent or consistency.

“What we want to avoid, as conscientious consumers, are the ingredients in sunscreen that are going to cause other health effects,” explains Lindsay Coulter, the David Suzuki Foundation’s resident Queen of Green, by phone.

But Coulter notes that there is a way out of this seemingly contradictory mess. Unlike for household cleaners, Health Canada requires manufacturers of sun-care products to list all components on the bottle, which makes it easy for shoppers to spot the good, the bad, and the must-avoid before heading to the checkout.

So, what’s one ingredient that consumers should avoid at all costs? According to Coulter, it’s fragrance, or “parfum”, a combination of any of more than 3,000 allergy-, migraine-, and asthma-triggering chemicals that imparts a synthetic odour to beauty and at-home products. These mixtures may even be present in “fragrance-free” or “unscented” items, where they go undetected in the presence of masking agents.

“If you avoid fragrance in your sunscreen and all your cosmetics, you’re probably going to avoid a bunch of other harmful chemical ingredients as well,” says Coulter. “It’s in almost everything, and almost always one of the last ingredients on every list.”

Coulter also identifies oxybenzone—a chemical additive that has been shown to interfere with the function of endocrine systems—and retinol palmitate, a form of vitamin A that may assist in the growth of skin tumours, as hazardous sunscreen components. A number of these chemicals are also bio-accumulative (meaning they can build up in the body) and may pose a threat to our waters and marine life.

To get the most out of your sunscreen, opt for mineral-based products that use zinc oxide, like the Alberta-based Rocky Mountain Soap Company’s new Vanilla Coconut Natural Sunscreen ($22 at Rocky Mountain Soap Company [various locations]) or Green Beaver’s Natural Mineral Sunscreen ($21.99 at Finlandia Pharmacy [1111 West Broadway]).

These creams go on white—like the stuff that lifeguards slather onto their noses—creating a physical barrier against all three types of UV rays (UVA, UVB, and UVC), while not damaging our ecosystem once traces of them inevitably end up in the water.

Whatever you do, Coulter stresses, just stay away from the click-and-mist styles. “It’s best to just avoid spray sunscreens for adults and children,” she says, “because there’s a risk of actually inhaling those nanoparticles, which will go straight to your lungs and into your bloodstream.”