Sunscreen is ever important in protecting your skin against the danger of ultraviolet radiation in the sun's rays. Sunburns can lead to premature aging, common skin cancer and even melanoma. The link between excessive sun exposure and skin cancer is even stronger than the link between smoking cigarettes and lung cancer. And though we all age with time, photoaging is a distinct and avoidable effect of sun exposure that manifests in increased fine lines and wrinkles, dyspigmentation (white and dark splotches), and roughened texture. Both chemical and mineral sunscreens can prevent photoaging.
What are the major categories of sunscreens?
Chemical sunscreens are also known as organic sunscreens. They are the opposite of mineral sunscreens, also known as inorganic sunscreens, photoblockers or physical blockers. The two differ in how their ingredients work, how they look when they're applied, how often they cause allergic reactions and how far in advance they need to be applied before sun exposure.
Chemical sunscreens are often referred to as "absorbers". The active ingredients are carbon-based compounds undergo a chemical reaction with the skin that allows them to convert UV rays into heat, which is then released into the environment. Because the active ingredients in chemical sunscreens are carbon-based, they are considered organic. But that doesn't mean they are the best choice for you. Some common active ingredients in this category are oxybenzone, avobenzone, octinoxate, homosalate, octisalate and octocrylene. Often many of these ingredients will be combined into one product as they offer different protection against different parts of the ultraviolet spectrum. Some are better at blocking UVA, and others are better at blocking UVB.
Mineral sunscreens have more familiar names, like titanium oxide, zinc oxide and iron oxide. These are sometimes referred to as "reflectors" since they cause the UV not to be absorbed into the skin. They form a protective barrier on the skin and reflect harmful rays. These active ingredients are commonly found naturally in the environment.
Because the active ingredients in chemical sunscreens are carbon-based, they are considered organic. But that doesn't mean they are the best choice for you.
Comparison of Chemical and Mineral Sunscreens
First, what are the major advantages and disadvantages of chemical sunscreens?
Chemical sunscreens absorb quickly into the skin and often have an invisible finish which is lightweight and sheer (that is, thin or transparent). This is what led to their popularity in people with skin of color and universal favor amongst consumers. They also perform better on consumer tests showing longer-lasting protection from UV rays, though this may be influenced by factors such as price, lack of white cast, and amount applied by the consumer.
The major criticisms of chemical sunscreens are threefold. First, selfishly, they can cause allergic reactions and flares of acne, rosacea and melasma. They require advance application - they can take 30 minutes after application to become active, and may people don't like to wait indoors after applying sunscreen before going outside. They have also come under ethical scrutiny for potentially eroding coral reefs in the ocean.
So what are the strengths and weaknesses of mineral sunscreens?
Mineral sunscreens are more gentle, making them ideal for those with sensitive skin. They are regarded as more environmentally friendly and ideal for babies and children. They also offer immediate protection as soon as they are applied, and many studies have shown they last longer in direct ultraviolet exposure. They're usually broad-spectrum (i.e. protecting against both UVA and UVB).
The major downside to mineral-based sunscreens is that they tend to leave a white cast on the skin and may be difficult to fully blend in. This decreases their popularity in people of color. Their function also depends on having a film protecting the skin - they can rub off, sweat off and rinse off easily, in contrast to chemical sunscreens which last longer when wet. And they can still cause acne breakouts and allergic reactions, though much more rarely.
A popular analogy is that mineral sunscreens are like a healthy meal and chemical sunscreens are like fast food. But any sunscreen is better than skipping altogether. Though the FDA recommends broad-spectrum sunscreen with SPF 15+, most dermatologists recommend SPF 30 or higher and reapplication every 2 hours.
To complicate matters more, because chemical sunscreens are cheaper they are often included as part of a product in order to boost protection in a certain part of the UV spectrum or to provide broader UV coverage. For this reason many products on the market contain a combination of mineral and chemical sunscreens. Sunscreen purists and dermatologists have started recommending mineral-only sunscreens to their patients more frequently, though the best sunscreen for you is the one you'll use regularly. If you hate a white cast, you might avoid mineral sunscreens, and if you get allergic reactions you might avoid chemical ones. No two products are identical and it might take some trial and error to find the best one for your skin.