Sunscreen Vs. Sunblock - What's the Difference?

When people talk about physical sunblock and chemical sunscreens, I don't understand how they are different.  Which one works better? 

Doctor Answers 4

Sunscreen and sunblock - it depends whether you want a tan or not

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Kenneth A. Arndt, MD, clinical professor of Dermatology at Harvard Medical School, Boston, wrote in the current "Bottom Line Personal" that sunscreen and sunblock are not the same.

Sunblock is opaque and blocks almost all of the sun's UVA and UVB rays. It consists largely of zinc oxide and titanium dioxide. Sunblock does not have to be reapplied every few hours.

Sunscreens are less visible on the skin and are designed to protect against UVA, UVB, or both. They do allow some radiation through and need to be reapplied every few hours because their ingredients break down after exposure to sunlight. If you use sunscreen, it is better to use one that has a high SPF, put on a lot, and reapply every two to three hours.

The best way to keep your skin young is to avoid excessive sun damage, and establish the habit of wearing sun protection. The days of baby oil and iodine are over.

Have a fun summer!

Encino Facial Plastic Surgeon
4.8 out of 5 stars 36 reviews

Sunblock v. Sunscreen

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The term "sunblock" has been misleading and will soon be done away with.

The question of chemical versus physical block is important. Chemical sunscreens are often unstable after exposure to UV light and degrade over time. Some of the better spectrum coverage ingredients include Avobenzone (Parsol 1789) and mexoryl / helioplex / ecamsule.

The better physical blocks are zinc oxide and titanium dioxide with zinc being superior in broad spectrum protection. These physical blocks reflect and scatter light and act as a mirror on your skin to block entry of UV into the skin.

Look for SPF 30, which will block 97% UV rays but also look for zinc oxide in greater than 3% to provide coverage of UVA light and better overall protection.

Shawn Allen, MD
Boulder Dermatologist

Choose a Physical Sunscreen Which Blocks UVA and UVB Rays

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Chemical sunscreens are probably the most commonly used sunscreens. There are many different ingredients used in chemical sunscreens to keep track of, and they can be irritating to the skin.

Physical sunscreens have been referred to as sunblocks, because they reflect the sun's rays away from the body. They come in two ingredients: zinc oxide and titanium dioxide. 

These physical blockers have come a long way since the white cream on the lifeguard's nose. They are available in tinted cosmetically elegant creams and also in powder form.

The most important thing to remember is to use a sun protection product that blocks both UVA and UVB rays, and to use it in whatever form that will make you want to wear it every day.

All of the sunscreens we carry are physical sunscreens. I explain more in the video.

Best Recommendations For Sunscreen

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I recommend that you look for a sunscreen that protects you from UVA and UVB radiation. UVA rays are longer wavelengths tat penetrate more deeply into the skin are contribute to the development of skin cancer (and wrinkles), whereas UVB rays are shorter, cause burning of the skin, and also lead to skin cancer. Either a physical or chemical sunscreen can be used, the former being best for those with sensitive skin. Look for products that have SPF 30 or higher. Most people do not apply enough product to render themselves as protected as the package indicates. A good rule of thumb: a shotglassful of sunscreen should be used to cover the body at each application and the product should be reapplied every 2 hours when outside.

Tina S. Alster, MD
Washington Dermatologic Surgeon
5.0 out of 5 stars 1 review

These answers are for educational purposes and should not be relied upon as a substitute for medical advice you may receive from your physician. If you have a medical emergency, please call 911. These answers do not constitute or initiate a patient/doctor relationship.