Sunscreens are crucial for preventing sun overexposure, wrinkles, sun spots and skin cancer. But it’s not always easy to know which ones work best and which to trust.
Last summer, the Environmental Working Group released a report finding that more than 1,800 sunscreens contain chemicals such as oxybenzone (which may disrupt hormones) and retinol. BU Today asked several dermatologists for their top tips on picking the right formulas.
Ultraviolet (UV) Rays
UV rays cause damage to the skin’s layers and disrupt the skin’s natural radiance. They also contribute to the aging process and play an important role in the development of sunburn and skin cancer. Sunscreen contains ingredients that either absorb or scatter the harmful rays. Mineral sunscreens, such as titanium dioxide and zinc oxide, create a physical barrier on the skin and reflect UV rays away from the skin. These sunscreens typically have SPF numbers of 30 or higher.
Chemical sunscreens contain molecules that suck up the UV rays. They are often made with a combination of different chemicals, such as oxybenzone and avobenzone. When the sun’s UV rays hit these molecules, their electrons get excited and then they release relatively harmless amounts of energy in the form of heat.
Both kinds of sunscreens absorb UV rays from the front and back of the sun. However, the ozone layer prevents some UVB rays from reaching the Earth’s surface, so the UVB protection on a sunscreen label is usually only about 10% of its SPF rating.
There are many different ways that UV radiation can reach your skin, including reflected rays and direct transmission through the atmosphere. UV radiation is also more intense at high altitudes, where there is less of the atmosphere to absorb it. UV exposure is also increased by the time of day and season. Repeated UV exposure doubles the risk of developing the deadliest form of skin cancer, melanoma.
Chemicals
Sunscreens use chemicals to protect your skin from the sun’s harmful UV rays. In the United States, any sunscreen that makes a claim about protecting you from sunburn or reducing the risk of skin cancer and aging must be regulated as an over-the-counter drug by the FDA (Food and Drug Administration).
Chemical sunscreens use carbon-containing molecules like oxybenzone, octinoxate, homosalate, and octisalate to absorb UV rays and disperse them into heat energy. They can be either organic or inorganic and are usually combined to give broad-spectrum protection.
Inorganic sunscreens rely on titanium dioxide and zinc oxide to reflect and disperse UV rays. They don’t offer the same level of protection as chemical sunscreens, but are still better than nothing.
Chemical sunscreens have been linked to negative outcomes in humans, such as endocrine problems and skin cancer. They can also pose a threat to marine life in high concentrations. For example, benzene — a carcinogen – can build up in the tissues of marine organisms and potentially affect their health. Benzene is used in the production of plastics, rubber, pesticides and other products and is found naturally in gasoline, crude oil and cigarette smoke. Benzene can also cause leukemia and anemia in people who are exposed to it for long periods of time. The chemical retinyl palmitate is another concern because it may accelerate skin aging.
Physical Blockers
Sunscreen and sunblock contain active ingredients that help protect the skin from UVA (long wave ultraviolet A) and UVB (short wave ultraviolet B) rays, which cause aging and sunburns. Chemical sunscreens absorb into the skin and convert UV rays to heat, which is then released from the skin. Active ingredients include oxybenzone, avobenzone, octocrylene and homosalate. Physical sunblock sits on top of the skin and reflects or blocks the rays, with titanium dioxide and zinc oxide being common ingredients. These products tend to be less irritating and offer better year-round protection.
Both types of sunscreen provide effective protection against UVA rays as long as they’re broad spectrum and have a high SPF rating. But the type you choose may depend on your skin, says dermatologist and Mohs surgeon David Harvey. He explains that physical blockers may leave a white or chalky appearance on darker skin tones, while chemical sunscreens can be more comfortable and blend in well.
A physical sunscreen can also be difficult to find for people with oily skin, and it can take longer to rub in and start working than a chemical option. But there are now physical sunscreens with a lightweight formula that doesn’t leave a white appearance, and there are also chemical sunscreens that have been specifically formulated to not irritate the skin.
Other Ingredients
Many sunscreens contain more than one active ingredient in order to provide adequate protection from the sun’s UV rays. These ingredients can be either organic or inorganic and come in a variety of forms, from titanium dioxide to zinc oxide. The American Academy of Dermatology divides these sunscreen ingredients into two categories: chemical and physical1.
Chemical sunscreens protect against UV-B rays that cause sunburn, while the physical molecules in mineral products (such as titanium dioxide and zinc oxide) block both UV-A and UV-B rays2.
According to the FDA, chemical sunscreen ingredients such as cinoxate, dioxybenzone, ensulizole, homosalate, meradimate, octocrylene, octisalate, padimate O, sulisobenzone, and oxybenzone are considered safe by the FDA when used according to the manufacturer’s instructions3.
However, some of these chemicals have been found to penetrate the skin, causing cell damage and possibly cancer4.
The FDA is asking sunscreen manufacturers for more information about these chemicals. In the meantime, both Michele and Schlosser advise that consumers should read sunscreen labels carefully, looking for natural, green or organic options. They also recommend choosing a water-resistant sunscreen and using a broad spectrum formula. They also advise against combining insect repellent with sunscreen, as a DEET-containing product can reduce the effectiveness of a sunscreen5.