What The Difference Between Physical And Chemical Sunscreens?
Active ingredients that give sunscreens their sun-screening power come in two forms, physical (or mineral) and chemical (or organic). Wait, chemical sounds so gross...but those are the organic sunscreens? It’s confusing. Let’s break it down.
In the skincare industry, few things are harped on (and on and on) as wearing sunscreen. It’s the one essential you should never leave the house without applying, whether you have a skincare routine or not. It’s the start-while-you’re-young answer to aging and skin cancer prevention. It’s your excuse to spend two more hours soaking up rays then the recommended daily 10 minutes.
And it’s a multi-million-dollar industry in the United States because people got the hint and are slathering on sunscreen more than ever before. (1)
So much so that certain common active ingredients widely used in sunscreens are showing up in everybody's bloodstreams, mother’s breast milk and our ocean’s coral reefs. Mission accomplished: Sunscreen is everywhere and on everyone.
But have we gone too far? is your sunscreen doing more harm than good? Active ingredients that give sunscreens their sun-screening power come in two forms, physical and chemical, and they work very, very differently.
Chemical Sunscreens Work Like a Sponge
They soak up harmful sun rays so your skin doesn’t have to
Chemical sunscreens, unsurprisingly, rely on chemical active ingredients to get the job done. They work by absorbing and scattering UV rays, but it turns out they can also absorb into your bloodstream. When the sun comes into contact with skin covered in a chemical sunscreen, a chemical reaction turns harmful rays into heat that dissipates back into the air.
There are plenty of reasons to be skeptical of the safety of chemical sunscreens. Some of the most common active ingredients used in chemical sunscreens have been linked to hormone disruption in humans and coral reef bleaching in oceans. Moreover, most chemical sunscreens require a cocktail of chemicals, not just one or two, to provide protection from both UVA and UVB rays. That means they’re more likely to be irritiating to sensitive skin. (2, 3, 4, 5)
Pros of Chemical Sunscreen
- Less white residue
- Spreads more easily
- Tends to stay on better
Cons of Chemical Sunscsreen
- Takes 20 minutes to start working
- Can penetrate through the skin
- Not exactly environmentally friendly
- Can be pore-clogging & more irritating
Chemical Sunscreens Are Technically Organic Sunscreens
Sounds liks an oxymoron
In an era where chemical is the skincare villain du jour and organic the straight and narrow path back to saving face, it feels unnatural to equate organic sunscreens with chemical sunscreens. But it’s true. An organic sunscreen is one that uses carbon-based chemicals. This gets more confusing on the consumer end when brands talk about physical sunblocks as organic because they have fewer ingredients on the label.
Physical Sunscreens Are Mineral-Based Blockers
Instead of absorbing and scattering sun rays, physical sunblocks work like a shield that deflects them off the skin. The most widely used mineral filters in physical sunscreens are zinc oxide and titanium dioxide, often in nanoparticles to prevent that familiar white film from forming. When used together, zinc oxide and titanium dioxide create broad-spectrum sunscreen that protects from both types of ultraviolet radiation, UVA and UVB. (6, 7)
- Don’t absorb into the skin
- Gentler on sensitive skin
- Start working immediately
- More likely to leave chalky, white residue
- Thicker and harder to spread
- Rub off more easily
Come Again? Nano...what?
Nanoparticles are microscopic which makes them attractive to sunscreen developers. The smaller the mineral filter particle, the more transparent the sunscreen is on the skin. The flip side of that coin, though, is that larger particles offer better UVA protection but people are less likely to buy (or apply) sunscreen that leaves a white tint.
To put nano-scale into perspective, one strand of hair is about 80,000 nanoparticles thick. Watchdogs like the Environmental Working Group and the Europeans Union’s scientific committee on cosmetics have raised concerns that there’s not enough data to measure the long-term health effects of nanoparticles potentially small enough to absorb through the skin. Yet, several studies already conducted haven’t found much compelling evidence that nanoparticles cross the skin barrier in significant amounts. (8, 9)
Which Type of Sunscreen is Worse for the Environment?
Trick question. Both have their drawbacks, tbh.
Both chemical and physical UV-filters have been detected in coastal waters, according to the ICRI. Plenty of data to demonstrates that oxybenzone and other chemical filters are contributing to coral bleaching, and some studies have supported that zinc oxide and titanium dioxides nanoparticles are entering marine environments. In both cases, there are more unknowns than knowns, but playing it safe now might make for a less-sorry humanity later. (10)
Nanoparticles & Photoactivity
Oxidative stress isn’t just bad for your skin, it’s hard on marine life, too
Decreased particle size means increased reactivity. Nanomaterials are highly reactive thanks to a surface-area-to-mass ration that makes chemical reactions more likely to occur. Because of this, sunscreens with nanoparticles, usually physical sunscreens with zinc oxide, aren’t just less effective against UVA rays but also more photoactive. Photoactive ingredients are less stable in sunlight and more likely to interact and react with ultraviolet radiation, producing more reactive oxygen species (ROS) and free radicals (which you can read more about here). Free radicals spell trouble for both marine life and your skin because they cause oxidative stress. (11 12, 13) 13)
Oxybenzone & Coral Bleaching
Probably the most studied of all the understudied active ingredients used in sunscreens, oxybenzone is considered one of the most hazardous — for people and the planet. Even though it’s showing up in mother’s breast milk, is a known hormone disruptor and causes allergic reactions on the skin, oxybenzone is widely used in sunscreens. Thanks to its high rate of penetration, oxybenzone is present in the body of nearly every American studied, but it’s showing up somewhere else of great concern: our oceans. (14, 15)
According to the ICRI, nearly 20,000 tons of oxybenzone is finding its way off our skin or through our water treatment facilities into marine life. Although concentration varies from case-to-case and ocean-to-ocean, studies have shown that oxybenzone induces coral bleaching and even coral death. Research has shown that oxybenzone not only damages coral but because it's an endocrine disruptor also deforms coral larvae and inhibits coral reproductive success.
Bottom line: even though oxybenzone is in about ⅔ of chemical sunscreens there are better options out there for you and the environment and plenty of reasons to opt out of oxybenzone — just like REI is doing by 2020 with, hopefully, more retailers to follow suit. (16, 17)